Automatic air-deeding mechanism for pneumatic tire

ABSTRACT

To provide an automatic air-feeding mechanisms which can produce a large amount of compressed air with a small number of rotations of a wheel body and with a small force. The automatic air-feeding mechanisms has first and second compressed air producing sections  1   a  and  1   b , and pneumatic tire compressed air supply passages  2   a  and  2   b  for introducing the compressed air produced in the compression air producing sections to a pneumatic tire. The first and second compressed air producing sections  1   a  and  1   b  are attached to a hub drum  102   a  of the hub  102  at positions 180° apart from each other. When the wheel body is rotated, the first and second compressed air producing sections 1 a  and 1 b  alternately produce compressed air.

CROSS REFERENCE TO RELATED APPLICATIONS

The disclosure of Japanese Patent Application No. 2003-090079 (filed onMar. 28, 2003) and International Application No. PCT/JP/2003/015820(filed on Dec. 10, 2003) including the specification, claims, drawingsand abstract are incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to an automatic air-feeding mechanism fora pneumatic tire which can produce compressed air and supply it to thepneumatic tire when a wheel body is rotated about an axle.

BACKGROUND ART

Pneumatic tires holding air are mounted on wheels of automobiles orbicycles. Even if air is pumped into such a pneumatic tire until the airpressure therein reaches a specific level, the air gradually escapestherefrom and the air pressure therein gradually decreases over time.When the air pressure is too low, it adversely affects the ride qualityor handling. Thus, when the air pressure becomes much lower than the aspecific level, air should be supplied into the pneumatic tire with anair supply device such an air pump.

However, a considerable force is required to operate an air pump to feedair into a pneumatic tire. Thus, it is difficult for a person withoutmuch strength to operate an air pump to feed air into a pneumatic tire.

DISCLOSURE OF THE INVENTION

The present invention has been made in view of the above circumstances,and it is, therefore, an object of the present invention to provide anautomatic air-feeding mechanism for a pneumatic tire with which air canbe automatically fed into a pneumatic tire by the rotation of thepneumatic tire about the axle without using an air pump or the like whenthe air pressure in the pneumatic tire becomes lower than a specificvalue.

Another object of the present invention is to provide an automaticair-feeding mechanism for a pneumatic tire having a compressed airproducing section which rainwater or the like can hardly enter.

Another object of the present invention is to provide an automaticair-feeding mechanism for a pneumatic tire which can produce a largeamount of compressed air with a small number of rotations of the wheelbody and with a small force.

Another object of the present invention is to provide an automaticair-feeding mechanism for a pneumatic tire which can produce asufficient amount of compressed air in a short travel distance so thatit can supply compressed air to a pneumatic tire of a vehicle which isdriven too short a distance to rotate a wheel a sufficient number oftimes during normal use such as a wheelchair.

Another object of the present invention is to provide an automaticair-feeding mechanism for a pneumatic tire which can produce a largeamount of compressed air with a small number of rotations of the wheelbody with a small force and which can supply compressed air to apneumatic tire and a part of the vehicle other than the pneumatic tirewhen the vehicle is running.

Another object of the present invention is to provide an automaticair-feeding mechanism for a pneumatic tire which can reduce theresistance to the rotation of the wheel body about the axle.

The automatic air-feeding mechanism for a pneumatic tire according tothe present invention is an automatic air-feeding mechanism for apneumatic tire for automatically supplying air to a pneumatic tiremounted on a wheel body rotatable about an axle of a vehicle, whichcomprises:

a compressed air producing section for producing compressed air when thewheel body is rotated about the axle, in which the compressed airproduced in the compressed air producing section is supplied to thepneumatic tire.

Although the features of this invention can be expressed as above in abroad sense, the constitution and content of this invention, as well asthe object and features thereof, will be apparent by reference to thefollowing disclosure taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of a wheel of a bicycle provided with an automaticair-feeding mechanism according to a first embodiment of the presentinvention;

FIG. 2 is an enlarged cross-sectional explanatory view taken along theline II-II in FIG. 1;

FIG. 3 is a cross-sectional explanatory view taken along the lineIII-III in FIG. 2;

FIG. 4 is an enlarged cross-sectional explanatory view illustratingessential parts of second and third air passages;

FIG. 5 is a cross-sectional view taken along the line V-V in FIG. 4;

FIG. 6 is a cross-sectional explanatory view illustrating the state inwhich a sliding part of a compressed air producing section has been slidfrom the position shown in FIG. 2 to its uppermost position;

FIG. 7 is a cross-sectional explanatory view taken along the lineVII-VII in FIG. 6;

FIG. 8 is an enlarged cross-sectional explanatory view taken along theline VIII-VIII in FIG. 1;

FIG. 9 is a side view of a wheel of a wheelchair provided with anautomatic air-feeding mechanism according to a second embodiment of thepresent invention;

FIG. 10 is an enlarged cross-sectional explanatory view taken along theline X-X in FIG. 9;

FIG. 11 is a cross-sectional explanatory view taken along the line XI-XIin FIG. 10;

FIG. 12(A) is a front view of a slider;

FIG. 12 (B) is a cross-sectional view taken along the line XII-XII inFIG. 12(A);

FIG. 13(A) is a partial enlarged cross-sectional view of a cam;

FIG. 13(B) is a cross-sectional view taken along the line XIII-XIII inFIG. 13(A);

FIG. 14 is a cross-sectional explanatory view showing the state in whicha slider of a first compressed air producing section is being slidtoward its uppermost position and a slider of a second compressed airproducing section is being slid toward its lowermost position from thepositions shown in FIG. 11;

FIG. 15 is a cross-sectional explanatory view showing the state in whichthe slider of the first compressed air producing section has been slidto its uppermost position and the slider of the second compressed airproducing section has been slid to its lowermost position from thepositions shown in FIG. 14;

FIG. 16 is a cross-sectional view taken along the line XVI-XVI in FIG.15;

FIG. 17 is a cross-sectional explanatory view showing the state in whichthe slider of the first compressed air producing section is being slidtoward its lowermost position and the slider of the second compressedair producing section is being slid to its uppermost position from thepositions shown in FIG. 16;

FIG. 18 is a side view of a bicycle provided with an automaticair-feeding mechanism according to a third embodiment of the presentinvention;

FIG. 19 is an enlarged cross-sectional explanatory view of an essentialpart of the automatic air-feeding mechanism according to the thirdembodiment;

FIG. 20 is a vertical cross-sectional explanatory view of a rotaryconnection member;

FIG. 21 is a horizontal cross-sectional explanatory view of the rotaryconnection member;

FIG. 22 is an enlarged cross-sectional view of a part of a saddle of abicycle provided with the air-feeding mechanism according to the thirdembodiment;

FIG. 23 is an explanatory view of an automatic air-feeding mechanismaccording to a fourth embodiment of the present invention;

FIG. 24 is an enlarged cross-sectional explanatory view of a brakedevice of a bicycle provided with an automatic air-feeding mechanismaccording to the fourth embodiment of the present invention;

FIG. 25 is an enlarged cross-sectional explanatory view showing thestate in which a brake wire has been operated to bring a brake shoe intocontact with a drum from the state shown in FIG. 24.

FIG. 26 is a cross-sectional explanatory view of an embodiment in whichboth first and second pin insertion holes have a sliding groove; and

FIG. 27 is an explanatory view illustrating the calculation of thedistance which a retention pin of a piston member has to be moved withrespect to a piston retaining part when a hub is rotated.

BEST MODE FOR CARRYING OUT THE INVENTION

Description will be hereinafter made of the embodiments of the presentinvention in detail with reference to the drawings. FIG. 1 is a sideview of a wheel of a bicycle provided with an automatic air-feedingmechanism for a pneumatic tire according to a first embodiment of thepresent invention, FIG. 2 is an enlarged cross-sectional explanatoryview taken along the line II-II in FIG. 1, and FIG. 3 is across-sectional explanatory view taken along the line III-III in FIG. 2.

In this embodiment, the automatic air-feeding mechanism for a pneumatictire is provided on a front wheel 100 of a bicycle. The wheel 100 of thebicycle provided with the automatic air-feeding mechanism for apneumatic tire has an axle 101 and a wheel body 110 rotatable about theaxle 101.

As shown in FIG. 2, the axle 101 has an axle body 101 d having threads101 a on its outer periphery, ball pushers 101 b and 101 b threaded onboth right and left sides of the axle body 101 d and secured thereto,and a pipe-like positioning member 114. The positioning member 114 willbe described later.

As shown in FIG. 1, the wheel body 110 has a hub 102, a pneumatic tire103 and the automatic air-feeding mechanism. As shown in FIG. 2, the hub102 has a cylindrical hub drum 102 a and right and left supporting parts102 b and 102 c fixed to the right and left sides, respectively, of thehub drum 102 a.

The supporting parts 102 b and 102 c are fitted on the outer peripheryof the hub drum 102 a and attached thereto in a non-rotatable manner.The right and left supporting parts 102 b and 102 c fixed to the rightand left sides of the hub drum 102 a define a partitioned space 111separated from the exterior within the hub 102.

Ring-shaped waterproof packings 112 and 112 are interposed between thesupporting parts 102 b and 102 c and the hub drum 102 a so that watercannot enter the partitioned space 111 through gaps between thesupporting parts 102 b and 102 c and the outer periphery of the hub drum102 a.

Each of the supporting parts 102 b and 102 c has a steel ball receivingpart 102 d extending radially inward therefrom for rotatably receivingsteel balls, and a plurality of steel balls 107, . . . and 107 arerotatably received in each steel ball receiving part 102 d. Axle holes102 e and 102 e for receiving the axle 101 are formed radially insidethe steel ball receiving parts 102 d.

As shown in FIG. 4, the axle 101 extends through the axle holes 102 e,and the steel balls 107, . . . and 107 are rotatably disposed, togetherwith grease (not shown), between the ball pushers 101 b and 101 bthreaded on the axle body 101 d and the steel ball receiving parts 102d, whereby the steel ball receiving parts 102 d are rotatably supportedon the axle body 101 d via the steel balls 107, . . . and 107. The hub102 is thereby rotatable about the axle 101.

As shown in FIG. 2 and FIG. 3, each of the supporting parts 102 b and102 c has a flange 102 g with a plurality of spoke holes 102 f, . . .and 102 f extending radially outward therefrom. The proximal ends ofspokes 104 (shown in FIG. 1) are engaged in the spoke holes 102 f, . . .and 102 f of the flanges 102 g. The distal ends of the spokes 104 areengaged with a rim 105 as shown in FIG. 1. The rim 105 is thereby fixedto the hub 102 and rotatable about the axle 101.

The pneumatic tire 103 is removably engaged on the rim 105, so that thepneumatic tire 103 is rotatable together with the rim 105 about the axle101. As shown in FIG. 8, an air tube 103 b as an air holding part forholding air therein is provided in the pneumatic tire 103.

The air tube 103 b has a valve 106 through which air is fed in andejected. The valve 106 has a cylindrical shape, and has an air inlet 106a at the lower end as seen in the drawing and a valve hole 106 b at theupper end as seen in the drawing. The valve hole 106 b is closed by acylindrical check valve 106 c of a synthetic rubber fitted on the outerperiphery of the valve 106.

The valve 106 is received in a cylindrical valve fitting 103 c attachedto the air tube 103 b, and a valve fixing nut 106 d threaded on thevalve fitting 103 c prevents the valve 106 from coming off. When air isfed through the air inlet 106 a against the elasticity of the checkvalve 106 c closing the valve hole 106 b with an air pump or the like,the air forcibly opens check valve 106 c and flows into the air tube 103b. After air has been fed into the air tube 103 b, the check valve 106 ccloses the valve hole 106 b because of its elasticity. The air in theair tube 103 b is thereby prevented from escaping through the valve hole106 b.

The check valve 106 c, the valve fitting 103 c and the valve fixing nut106 d, which are the same as those of an ordinary air tube 103 b for abicycle wheel, are not limited to those as described above and may bemodified as needed. The automatic air-feeding mechanism of the presentinvention does not necessarily require a valve 106 for a pneumatic tire103 and applicable to a pneumatic tire 103 without a valve 106. When avalve is used, the valve is not limited to an English valve (Woodsvalve) as shown in FIG. 8. The valve may be an American valve (Schradervalve) or a French valve (Presta valve) when necessary.

The right and left sides of the axle 101 of the wheel 100 constituted asdescribed above are secured to the body of a bicycle by nuts 108 and 108(shown in FIG. 2). The wheel body 110 is thereby rotatable with respectto the body of the bicycle.

The automatic air-feeding mechanism will be next described. Theautomatic air-feeding mechanism of this embodiment has an air feedingsection for producing compressed air and feeding it to the pneumatictire. As shown in FIG. 2 and FIG. 3, the air feeding section has acompressed air producing section 1 for producing compressed air and apneumatic tire compressed air supply passage 2 for supplying compressedair produced in the compressed air producing section 1 to the pneumatictire 103.

The compressed air producing section 1 has a compression chamber 31 forcompressing air therein, a piston member 32 as a compressing element forcompressing the air in the compression chamber 31, an air intake port 4for introducing outside air into the compression chamber 31, andwaterproof mechanisms 51, 52, 54 and 55 for preventing water fromentering the compression chamber 31 through the air intake port 4.

The compression chamber 31 is formed in an inner casing 3 a having acircular cross-section. An outer casing 3 b having a circularcross-section is fitted over the outer periphery of the inner casing 3 ain a non-rotatable manner. The outer casing 3 b has hub attaching parts30 b and 30 b (shown in FIG. 3) at its proximal end. The hub attachingparts 30 b and 30 b are secured to the outer periphery of the hub drum102 a of the hub 102 by bolts 30 c and 30 c. The inner casing 3 a isthereby attached to the outer periphery of the hub drum 102 a of the hub102 via the outer casing 3 b and protruded outward from the outerperiphery of the hub drum 102 a of the hub 102.

A partition 7 is provided in the inner casing 3 a attached to the hub102 as described above. The interior of the inner casing 3 a ispartitioned into the compression chamber 31 on the lower side as seen inthe drawings and a hereinafter described communication supply passage 13b of the pneumatic tire compressed air supply passage 2 on the upperside as seen in the drawings by the partition 7.

The piston member 32 for compressing the air in the compression chamber31 constituted as described above has a rod-like piston rod 33 as anoperation element, a cam contact part 35 in contact with a cam face 91 aof a cam 9, which will be described later, and a cam retention partretained by the cam 9. The piston rod 33 is slidably inserted through arod guide member 38 made of a synthetic rubber and having a cylindricalshape in the inner casing 3 a, and the distal end of the piston rod 33,which is the upper end thereof as seen in FIG. 2, is located in thecompression chamber 31. The piston rod 33 in this state is disposedradially outside the cam face 91 a of the cam 9 such that the axis ofthe piston rod 33 and the axis of the compression chamber 31 generallycoincide with each other. A sliding part 34 is provided at the distalend of the piston rod 33.

The sliding part 34 has a diameter generally the same as the insidediameter of the compression chamber 31 and is slidable along the innerwall of the compression chamber 31 in the axial direction of thecompression chamber 31, in other words, a radial direction of the axle101 and the cam 9. The sliding part 34 has a ring-shaped packing 34 amade of a synthetic rubber.

The piston rod 33 extends through the rod guide member 38 in thecompression chamber 31 and a piston introduction hole 115 formed throughthe hub drum 102 a, and the proximal end of the piston rod 33, that is,the lower end thereof as seen in the drawings, is located in thepartitioned space 111 in the hub 102. The cam contact part 35 and thecam retention part is provided at the proximal end of the piston rod 33.

In this embodiment, the cam contact part 35 is constituted of a part ofthe outer periphery of a rotatable roller 37 as shown in FIG. 2. Morespecifically, the roller 37 is partially protruded between the pistonrod 33 and the cam face 91 a of the cam 9 from the piston rod 33 towardthe cam face 91 a of the cam 9, and rotatably attached to the piston rod33 by a retention pin 36. The outer periphery of that part of the roller37 protruded toward the cam face 91 a constitutes the cam contact part35. In this embodiment, the cam contact part 35 is formed on anextension q of the axis of the piston rod 33.

In this embodiment, the cam retention part is constituted of a part ofthe retention pin 36 for supporting the roller 37. More specifically,the retention pin 36, which extends through a pin insertion hole formedthrough the piston rod 33 and a pin insertion hole formed through theroller 37, is protruded to the left from the piston rod 33 and attachedto the piston rod 33. The protruded part 36 a of the retention pin 36constitutes the cam retention part retained by the cam 9.

The cam 9, around which the roller 37 travels, has a cam body 91 havingthe cam face 91 a having a circular cross-section and in contact withthe roller 37 on its outer periphery, and a piston retaining part 92 asan operation element retaining part for removably retaining the pistonmember 32. The piston retaining part 92 has a disk-like shape. Thepiston retaining part 92 has a cam body receiving hole 92 a forrotatably receiving the cam body 91 at the center thereof. The cam body91 is rotatably received in the cam body receiving hole 92 a, wherebythe piston retaining part 92 is located on the left side in the axialdirection on the cam face 91 a of the cam body 91.

The piston retaining part 92 has pin insertion holes 92 b, . . . and 92b for rotatably receiving the protruded part 36 a of the retention pin36 of the piston member 32 around the outer periphery of the cam bodyreceiving hole 92 a. The protruded part 36 a of the retention pin 36 isremovably inserted into one of the pin insertion holes 92 b, . . . and92 b. In this embodiment, three pin insertion holes 92 b, . . . and 92 bare formed circumferentially spaced at approximately 120° on a circleabout the axis of the cam body receiving hole 92 a of the pin supportingmember 92. The protruded part 36 a of the retention pin 36 may beinserted into any one of the pin insertion holes 92 b, . . . and 92 b.

The piston member 32 of the compressed air producing section 1 isremovably retained by the cam 9 via the retention pin 36. Thus, in thisembodiment, although there is not provided a piston rod urging coilspring for constantly pressing the roller 37 of the piston member 32against the cam face 91 a, since the piston member 32 is constituted ofa positive motion cam retained by the cam 9, the roller 37 of the pistonmember 32 can be in constant contact with the cam face 91 a and run onthe cam face 91 when the hub 102 is rotated. The piston member 32 is notnecessarily retained by the cam 9. A piston rod urging coil spring maybe provided so that the piston member 32 can be pressed in contact withthe cam face 91 a by the coil spring.

The cam 9 has an axle insertion hole 93 for receiving the axle 101 asshown in FIG. 3. The center 02 of the axle insertion hole 93 is aspecific distance away from the center O1 of the cam face 91 a.

The axle 101 is inserted through the axle insertion hole 93, and the cam9 is fixed to the axle 101 from both right and left sides thereof by camfixing nuts 44 and 44 as shown in FIG. 2. The cam fixing nuts 44 islocated at fixed positions with respect to the ball pushers 101 b by thepositioning member 114 provided on the axle 101. In this fixed state,the center O2 of the axle insertion hole 93 coincides with the center O3of rotation of the hub 102 as shown in FIG. 3.

Thus, the position on the cam face 91 a where the roller 37 of thecompressed air producing section 1 is in contact with the cam face 91 ain the state shown in FIG. 2 and FIG. 3 is a small-diameter point A,where the distance from the center O2 of the axle insertion hole 93 issmallest. As the circumferential distance from the small-diameter pointA is greater, the distance from the center O2 of the axle insertion hole93 is greater, and the distance is greatest at a large-diameter point B,which is the position 180° away from the small-diameter point A.

When the roller 37 is at the small-diameter point A on the cam face 91a, the sliding part 34 of the piston rod 33 is at a lowermost positionA1 in the compression chamber 31 and the capacity of the compressionchamber 31 is maximum as shown in FIG. 2 and FIG. 3. When the roller 37is at the large-diameter point B on the cam face 91 a, the sliding part34 of the piston rod 33 is at an uppermost position B1 in thecompression chamber 31 and the capacity of the compression chamber 31 isminimum as shown in FIG. 6 and FIG. 7.

The air intake port 4 of the compressed air producing section 1 isprovided to introduce air from outside into the compression chamber 31as described before. In this embodiment, the air intake port 4 is formedin the vicinity of the lowermost position Al in the movable range of thesliding part 34 of the piston rod 33, which is slidable in thecompression chamber 31 between the lowermost position A1 and theuppermost position B1, and extends from the outer periphery of the innercasing 3 a to the compression chamber 31 as shown in FIG. 2.

Since the air intake port 4 is formed in the vicinity of the lowermostposition A1 in the movable range of the sliding part 34 in thecompression chamber 31, when the sliding part 34 is slid from lowermostposition A1 to the uppermost position B1, the air in the compressionchamber 31 can be compressed without being allowed to escape through theair intake port 4 while the sliding part 34 is slid from a position justbeyond the air intake port 4 to the uppermost position B1. Since the airintake port 4 is provided at the position described above, there is noneed for a check valve for preventing air from escaping from thecompression chamber 31 through the air intake port 4 when the slidingpart 34 is slid to compress the air in the compression chamber 31. Theautomatic air-feeding mechanism is, therefore, simple in constructionand hence can be produced at low costs.

When the air intake port 4 is provided in the vicinity of the lowermostposition A1 in the movable range of the sliding part 34 in thecompression chamber 31, a negative pressure is created in thecompression chamber 31 when the sliding part 34 is slid from theuppermost position B1 toward the lowermost position A1 since air is notintroduced into the compression chamber 31 until the sliding part 34reaches the air intake port 4.

Thus, the resistance applied to the sliding part 34 when it is slid fromthe uppermost position B1 toward the lowermost position A1 is greaterthe resistance applied to the sliding part when the intake port 4 isprovided in the vicinity of the uppermost position B1 in the movablerange of the sliding part 34 so that a negative pressure cannot besubstantially created.

When the air intake port 4 is provided in the vicinity of the lowermostposition A1 in the movable range of the sliding part 34 in thecompression chamber 31, if the piston member 32 is not retained by thecam 9 and a piston rod urging coil spring as a compressing elementurging spring for urging the piston rod 33 in the direction from theuppermost position B1 toward the lowermost position A1 is provided sothat the sliding part 34 of the piston rod 33 can be slid from theuppermost position B1 to the lowermost position A1 by the urging forceof the coil spring, it is necessary to use a coil spring having anurging force which is large enough to slide the sliding part 34 againstthe negative pressure in the compression chamber 31.

However, when a coil spring with such a large urging force is used,since the sliding part 34 has to be slid against the urging force of thecoil spring when it is slid from the lowermost position A1 to theuppermost position B1, the resistance to the rotation of the hub 201about the axle 101 is large. Thus, when the air intake port 4 isprovided in the vicinity of the lowermost position A1 in the movablerange of the sliding part 34 in the compression chamber 31, it ispreferred that the piston member 32 is constituted of a positive motioncam retained by the cam 9 without using a piston rod urging coil springsince the resistance to the rotation of the hub 201 about the axle 101can be small so that the hub 201 can be rotated smoothly.

The position of the air intake port 4 is not limited to the positiondescribed above. For example, the air intake port 4 may be provided inthe vicinity of the uppermost position B1 in the movable range of thesliding part 34. In this case, however, a check valve has to beprovided, which results in an increase in the number of steps in theproduction process and the cost. Thus, in view of the simplicity of theautomatic air-feeding mechanism and the production costs, the air intakeport 4 is preferably provided in the vicinity of the lowermost positionA1 in the movable range of the sliding part 34 as in the aboveembodiment.

In this embodiment, the compressed air producing section 1 has awaterproof mechanism constituted of a first air passage 51, a rightaxle-gap air passage 52 as a second air passage extending from the firstair passage 51, a third air passage 54 extending from the right axle-gapair passage 52, and a seal member 55.

The first air passage 51 connects the air intake port 4 in air flowcommunication with the partitioned space 111 and guides the air in thepartitioned space 111 to the air intake port 4. In this embodiment, thefirst air passage 51 is constituted of a guide groove formed in theinner surface of the outer casing 3 b and extending from the air intakeport 4 to the partitioned space 111 of the hub 102.

The right axle-gap air passage 52 is a spatial passage formed throughthe right supporting part 102 b and constituted of an axle gap 52 abetween the inner surface of the axle hole 102 e of the right supportingpart 102 b of the hub 102 and the axle 101 extending through the axlehole 102 e, and steel ball gaps 52 b, . . . and 52 b between the steelballs 107 and.107 disposed between the ball pusher 101 b of the axle 101and the steel ball receiving part 102 d as shown in FIG. 4 and FIG. 5.

In this embodiment, a positioning member 114 is provided in the axlehole 102 e, so that the axle gap 52 a is defined between the innersurface of the axle hole 102 e and the outer periphery of thepositioning member 114.

The third air passage 54 is defined between the inner surface of acylindrical member 56 and the outer periphery of the axle 101 andcommunicates the right axle-gap air passage 52 with the outside as shownin FIG. 4.

More specifically, the cylindrical member 56 is made of a syntheticresin and has an engaging projection 56 a for attaching it to the rightsupporting part 102 b on the outer periphery of the left end thereof asshown in FIG. 4.

The engaging projection 56 a is fitted in an engaging groove 102 h ofthe right supporting part 102 b, whereby the cylindrical member 56 isattached to the right supporting part 102 d of the hub 102.

A waterproof packing 116 is interposed between the outer periphery ofthe cylindrical member 56 and the right supporting part 102 b so thatwater cannot enter the right axle-gap air passage 52 through a gapbetween the outer periphery of the cylindrical member 56 and the rightsupporting part 102 b.

The axle 101 extends through the cylindrical member 56 attached to theright supporting part 102 b of the hub 102 as described above, and thethird air passage 54 communicating the right axle-gap air passage 52with the outside is formed around the entire circumference of the axle101 between the inner surface of the cylindrical member 56 and the axle101. In this embodiment, the ball pusher 101 b of the axle 101 isdisposed inside the cylindrical member 56, and the third air passage 54is defined between the outer periphery of the ball pusher 101 b and theinner surface of the cylindrical member 56.

The third air passage 54 has a taper part 59 a on the outside (rightside in FIG. 4) defined by an inner surface of the cylindrical member56, which is tapered such that the inside diameter gradually increasestoward the outside on the right, and a small-diameter small-width part59 c inside the taper part 59 a (on the left side in FIG. 4) defined bya closed part 59 b extending radially inward from the taper part 59 aand having a small radial width L1. In this embodiment, the taper part59 a has a taper angle P of 10°.

The third air passage 54 also has a large-diameter small-width part 61defined by an inner surface of the cylindrical member 56 and a covermember 60 on the right side of the small-diameter small-width part 59 c.The cover member 60, which has a disk-like shape with a diameter greaterthan that of the small-diameter small-width part 59 c, is disposedradially inside the taper part 59 a of the cylindrical member 56 andsecured to the axle 101.

The large-diameter small-width part 61 having a radial width L2 which isgenerally the same as the width L1 of the small-diameter small-widthpart 59 c and a diameter greater than that of the small-diametersmall-width part 59 c is thereby defined between the outer periphery ofthe cover member 60 and the taper part 59 a of the cylindrical member56. Thus, in this embodiment, the third air passage 54 has twosmall-width parts 59 c and 61 with different diameters so that air canflow windingly because of the two small-width parts 59 c and 61. In thisembodiment, the width L1 of the small-diameter small-width part 59 c andthe width L2 of the large-diameter small width part 61 are bothapproximately 0.5 mm.

The seal member 55 seals a left axle-gap air passage 53 formed in thehub 102 from outside. The left right axle-gap air passage 53 is, as inthe case of the right axle-gap air passage 52, a spatial passageconstituted of an axle gap 53 a between the inner surface of the axlehole 102 e of the left supporting part 102 c of the hub 102 and the axle101 extending through the axle hole 102 e, and steel ball gaps 53 bbetween the steel balls 107 and 107 disposed between the ball pusher 101b and 101 b of the axle 101 and the steel ball receiving part 102 d asshown in FIG. 2.

The seal member 55 has a ring shape and made of a synthetic rubber asshown in FIG. 2. An fitting piece 55 a formed on the inner periphery ofthe seal member 55 is fitted in a fitting groove 101 c of the ballpusher 101 b, whereby the seal member 55 is attached to the ball pusher101 b. The outer periphery of the seal member 55 attached to the ballpusher 101 b as described above is in contact with the left supportingmember 102 c along its entire circumference. The seal member 55 therebyseals the left axle-gap air passage 53 from outside to prevent waterfrom entering the left axle-gap air passage 53.

The pneumatic tire compressed air supply passage 2 of the automaticair-feeding mechanism will be next described. The pneumatic tirecompressed air supply passage 2 is formed between the compressed airproducing section 1 and the pneumatic tire 103, and has thecommunication supply passage 13 b communicated with the compressionchamber 31 of the compressed air producing section 1, a pneumatic tirefeeding supply passage 13 a connected to the air tube 103 b of thepneumatic tire 103, and a connection supply passage 21 a connecting thecommunication supply passage 13 b and the pneumatic tire feeding supplypassage 13 a as shown in FIG. 2 and FIG. 3.

The communication supply passage 13 b is defined by the partition 7 onthe upper side in the compression chamber 31, as seen in FIG. 2, in theinner casing 3 a. A through hole 71 is formed through the partition 7,and the compression chamber 31 is connected in air flow communicationwith the communication supply passage 13 b through the through hole 71.

A check valve 40 is provided in the through hole 71. The check valve 40is provided as means for preventing air from flowing in reverse from thepneumatic tire compressed air supply passage 2 to the compressionchamber 31, and constituted of a ball valve 40 disposed on the side ofthe pneumatic tire compressed air supply passage 2 in this embodiment.The ball valve 40 has a ball 41, a ball receiving packing 42 having aring shape and made of a synthetic rubber for receiving the ball 41, anda ball urging coil spring 43 as urging means for urging the ball 41toward the ball receiving packing 42. The ball 41 is urged by the urgingforce of the ball urging coil spring 43 to close the through hole 71from the side of the pneumatic tire compressed air supply passage 2.

The connection supply passage 21 a is formed within a cylindricalconnection pipe 21. The proximal end of the connection pipe 21 is fittedin the communication supply passage 13 b of the inner casing 3 a. Theproximal end of the connection supply passage 21 a is thereby connectedin air flow communication with the communication supply passage 13 b.

The connection pipe 21 has a pressure adjusting section 12 forcontrolling the air pressure in the pneumatic tire compressed air supplypassage 2 as shown in FIG. 3. The pressure adjusting section 12 causesthe pneumatic tire compressed air supply passage 2 to function as aconstant pressure maintaining section for maintaining the air pressureat a constant level.

In this embodiment, the pressure adjusting section 12 has a cylindricalpart 12 a with an air discharge port 11 a, a valve element 12 b foropening and closing the air discharge port 11 a, and a constant pressurevalve urging coil spring 12 c as constant pressure valve urging meansfor urging the valve element 12 b.

The cylindrical part 12 a is attached to the side wall of the connectionpipe 21, and the air discharge port 11 a of the cylindrical part 12 acommunicates the connection supply passage 21 a with the outside so thatcompressed air in the connection supply passage 21 a can be dischargedto the outside through the air discharge port 11 a.

The constant pressure valve urging coil spring 12 c constantly urges thevalve element 12 b toward the connection supply passage 21 a. The valveelement 12 b thereby closes the air discharge port 1 a.

The pressure adjusting section 12 is not necessarily provided at theconnection supply passage 21 a and can be provided at any part of thepneumatic tire compressed air supply passage 2. Also, the pressureadjusting section 12 may be modified as needed. For example, thepressure adjusting section 12 may be constituted of a ball valve.

The pneumatic tire feeding supply passage 13 a is formed in a connectionpipe 14 having elasticity. The connection pipe 14 is attached to thedistal end of the connection pipe 21 with its proximal end fitted overthe connection pipe 21. The connection supply passage 21 a is therebyconnected in air flow communication with the pneumatic tire feedingsupply passage 13 a.

A pneumatic tire connecting part 16 is provide at the distal end of theconnection pipe 14, which is the end opposite from the end attached tothe connection pipe 21, and removably connected to the pneumatic tire103 as shown in FIG. 8. The pneumatic tire connecting part 16 has apacking 16 a, and a nut engaging piece 16 b engageable with the valvefixing nut 106 d of the air tube 103 b. The nut engaging piece 16 b isengaged with the valve fixing nut 106 d with the packing 16 a in contactwith an end of the valve 106. The pneumatic tire feeding supply passage13 a is thereby connected in air flow communication with the air tube103 b.

The operation of the automatic air-feeding mechanism for a pneumatictire of this embodiment will be described. The pneumatic tire 103 isrotated about the axle 101 from the state in which the sliding part 34is in the lowermost position A1 in the compression chamber 31 in thecompressed air producing section 1 and the sliding part 34 is in theuppermost position B1 in the compression chamber 31 in a secondcompressed air producing section 1 b as shown in FIG. 2 and FIG. 3 by,for example, riding the bicycle. When the hub 102 is rotated, the roller37 of the piston member 32 of the compressed air producing section 1 isrotated together with the hub 102 and runs on the cam face 91 a of thecam 9 from the small-diameter point A toward the large-diameter point B.

Then, the piston member 32 is pressed by the cam 9 and kept presseduntil the roller 37 of the piston member 32 reaches the large-diameterpoint B of the cam 9. At this time, the sliding part 34 is slid in thecompression chamber 31 along the inner wall thereof from the lowermostposition A1 to the uppermost position B1.

While the sliding part 34 is slid from the lowermost position A1 to theuppermost position B1, the air in the compression chamber 31 iscompressed up to a certain compression ratio.

If an urging coil spring, for example, is used to press the piston rod33 during the sliding of the sliding part 34 so that the proximal end ofthe piston rod 33 can be kept in contact with the cam face 91 a of thecam 9, the piston rod 33 has to be slid against the urging force of thecoil spring, causing a resistance to the rotation of the hub 102. Inthis embodiment, however, since the piston rod 33 is retained by the cam9 via the retention pin 36 and such an urging coil spring is not used,the piston rod 33 can be smoothly slid with a small force. Thus, theresistance to the rotation of the hub 102 is small.

When a force in the tangential direction of the cam 9 which the pistonrod 33 receives from the cam 9 is too large, the piston rod 33 pressesthe rod guide member 38 in the compression chamber 31 in one direction,making it difficult for the piston rod 33 to slide and causing wear ofthe rod guide member 38. As a result, the piston rod 33 is inclined withrespect to the axial direction of the compression chamber 31, whichmakes it more difficult for the piston rod 33 to slide. In thisembodiment, however, since the force components in the axial directionof the compression chamber 31 and a direction perpendicular theretowhich the piston rod 33 receives from the cam 9 can be considerablysmall, the wear of the rod guide member 38 can be reduced. Thus, evenwhen repeatedly used, the piston rod 33 can be constantly pressed andsmoothly slid in the axial direction of the compression chamber 31.

Then, when the roller 37 of the piston member 32 of the compressed airproducing section 1 reaches the large-diameter point B of the cam face91 a, the sliding part 34 of the piston rod 33 of the compressed airproducing section 1 reaches the uppermost position B1 as shown in FIG. 6and FIG. 7. By the movement of the sliding part 34, the air in thecompression chamber 31 of the compressed air producing section 1 iscompressed.

When the air in the compression chamber 31 of the compressed airproducing section 1 is compressed as described above, the ball 41 of thecheck valve 40 is pushed by the pressure of the compressed air in thecompression chamber 31. At this time, the ball 41 of the check valve 40receives the pressure caused by the air pressure in the pneumatic tirecompressed air supply passage 2 and the urging force of the ball urgingcoil spring 43. Thus, the pressure from the pneumatic tire compressedair supply passage 2 is smaller than the pressure from the compressionchamber 31, the ball 41 of the check valve 40 is moved to the side ofthe pneumatic tire compressed air supply passage 2 to open the throughhole 71. The compressed air in the compression chamber 31 is thereby fedinto the pneumatic tire compressed air supply passage 2 through thethrough hole 71.

Then, when the sliding part 34 is moved in the compression chamber 31from the uppermost position B1 to the lowermost position A1, the ball 41of the check valve 40 closes the through hole 71. The air in thepneumatic tire compressed air supply passage 2 is thereby prevented fromreturning into the compression chamber 31.

When the air pressure in the pneumatic tire compressed air supplypassage 2 filled with compressed air exceeds a specific level, the valveelement 12 b of the pressure adjusting section 12 is pushed to open theair discharge port 11 a against the urging force of the constantpressure valve urging coil spring 12 c by the air pressure in thepneumatic tire compressed air supply passage 2. The compressed air inthe pneumatic tire compressed air supply passage 2 is thereby dischargedto the outside through the air discharge port 11 a. Then, when the airpressure in the pneumatic tire compressed air supply passage 2 becomes aspecific level, the valve element 12 b is pushed by the urging force ofconstant pressure valve urging coil spring 12 c to close the airdischarge port 11 a.

The compressed air maintained at a specific pressure in the pneumatictire compressed air supply passage 2 enters the valve 106 of the airtube 103 b and pushes the check valve 106 c closing the valve hole 106 bfrom inside of the valve 106 as shown in FIG. 8. When the pressure onthe check valve 106 c from inside thereof caused by the air pressure inthe pneumatic tire compressed air supply passage 2 is greater than thetotal of the elastic force of the check valve 106 c and the pressure onthe check valve 106 c caused by the air pressure in the air tube 103 b,the air in the pneumatic tire compressed air supply passage 2 forciblyopens the check valve 106 c closing the valve hole 106 b from inside andflows into the air tube 103 b.

Then, when the pressure on the check valve 106 c caused by the airpressure in the pneumatic tire compressed air supply passage 2 becomesequal to the total of the elastic force of the check valve 106 c and thepressure on the check valve 106 c caused by the air pressure in the airtube 103 b, the air flow into the air tube 103 b is stopped.

After that, when the air pressure in the air tube 103 b is reduced overtime and the total of the elastic force of the check valve 106 c and thepressure on the check valve 106 c caused by the air pressure in the airtube 103 b becomes smaller than the pressure on the check valve 106 ccaused by the air pressure in the pneumatic tire compressed air supplypassage 2, the check valve 106 c closing the valve hole 106 b isforcibly opened from inside by the air pressure in the pneumatic tirecompressed air supply passage 2 and the air in the pneumatic tirecompressed air supply passage 2 flows into the air tube 103 b. The airpressure in the air tube 103 b is thereby maintained constant.

When the connection pipe 14 comes off the connection tube 21 or thepneumatic tire 103, or when the connection pipe 14 is broken, the valve106 of the pneumatic tire 103 can maintain the air pressure in thepneumatic tire 103. Although the cam 9 is fixed to the axle 101 and isnot moved, and the piston rod 33 runs on the cam face 91 a and changesthe position, the position of the piston rod 33 is not changed and theposition of the cam face 91 a is changed in FIG. 6 and FIG. 7 for theconvenience of explanation. This is the case in FIG. 12 and FIG. 13described later.

When the hub 102 is further rotated, the piston member 32 is pulled bythe cam 9 since the retention pin 36 is retained by the piston retainingpart 92 of the cam 9. Thus, the roller 37 is kept in contact with thecam face 91 a of the cam 9 and runs on the cam face 91 a from thelarge-diameter point B toward the small-diameter point A. At this time,the cam 9 pulls the left side of the piston rod 33 of the piston member32, which is at a distance from the extension q of the axis of thepiston rod 33. However, when the sliding part 34 is slid from theuppermost position B1 to the lowermost position A1, the sliding part 34can be slid by a force smaller than that required when the sliding part34 is slid from the lowermost position A1 to the uppermost position B1to compress air since compression of air is not conducted, and hence thepiton rod 33 can be pulled smoothly.

By the running of the roller 37, the sliding part 34 is moved in thecompression chamber 31 from the uppermost position B1 to the lowermostposition A1 and returns to the position shown in FIG. 2 and FIG. 3.

When the sliding part 34 of the piston rod 33 passes the air intake port4 during the slide from the uppermost position B1 to the lowermostposition A1, air is introduced from the partitioned space 111 of the hub102 into the compression chamber 31 through the first air passage 51 andthe air intake port 4.

When the air in the partitioned space 111 flows into the first airpassage 51, outside air is sucked into the partitioned space 111 throughthe right axle-gap air passage 52 as the second air passage 52 and thethird air passage 54.

At this time, since the third air passage 54 has the taper part 59 a,water Ml having entered the taper part 59 a can be moved to thelarge-diameter side of the taper part 59 a and discharged out of thethird air passage 54 by a centrifugal force created by the rotation ofthe hub as shown in FIG. 4. Also, the water Ml having entered the taperpart 59 a can be moved outward on the taper part 59 a and discharged outof the third air passage 54 by its own weight. In addition, since thetwo small-width parts 59 c and 61 with different diameters of the thirdair passage 54 make it difficult for the water Ml, which is derived fromrain or the like, to pass through the third air passage 54, it isdifficult for the water M1 to enter the right axle-gap air passage 52through the third air passage 54.

Even if water M1 derived from rain or the like enters the right axle-gapair passage 52 through the third air passage 54, it is difficult for thewater M1 to pass through the right axle-gap air passage 52 because thesteel balls 107, . . . and 107 and grease are disposed in the rightaxle-gap air passage 52. This makes it difficult for the water M1 toenter the partitioned space 111 of the hub 102 through the rightaxle-gap air passage 52.

Thus, only air and no water M1 is allowed to enter the partitioned space111 through the second and third air passages 52 and 54. As a result,only air can be sucked into the compression chamber 31 from thepartitioned space 111 through the first air passage 51, and rainwater orthe like is prevented from entering the compression chamber 31 togetherwith the air.

After that, when the hub 102 is rotated and the sliding part 34 of thepiston member 32 is slid in the compression chamber 31 in the samemanner as described above, the production of compressed air andintroduction of outside air are alternately repeated in the compressionchamber 31 and the produced compressed air is supplied into thepneumatic tire 103 as needed.

To remove the piston member 32 from the cam 9, the retention pin 36 ispulled to the right together with the piston rod 33 to remove it fromthe pin insertion hole 92 b. The piston member 32 can be thereby removedfrom the cam 9, and the inner casing 3 a defining the compressionchamber 31 or the piston rod 33 can be easily removed from the hub 102.Since the parts can be easily disassembled and replaced, maintenance canbe made easily.

Although the second air passage 52 is constituted of the right axle-gapair passage 52 and the third air passage 54 for communicating the rightaxle-gap air passage 52 with the outside is provided since the leftaxle-gap air passage 53 is sealed by the seal member 55 to isolate itfrom the outside in the above first embodiment, the present invention isnot limited thereto and may be modified as needed. For example, thesecond air passage may be constituted of the right axle-gap air passage52 and the left axle-gap air passage 53 without providing the sealmember 55, and third air passages 54 for the right axle-gap air passage52 and the left axle-gap air passage 53 may be provided. However, when athird air passage 54 as in the above embodiment is provided on bothsides of the hub 102, the cost is increased. Thus, in order to make itdifficult for water to enter the second air passage 54 and reduce theproduction costs, it is preferable to provide a third air passage 54only on the right or left side of the hub 102 and a seal member 55 onthe other side of the hub 102.

Although the third air passage 54 is formed by the cylindrical member 56secured to the hub 102 and the cover member 60 secured to the axle 101in the above first embodiment, the present invention is not limitedthereto and may be modified as needed. For example, the third airpassage 54 may be formed by only the cylindrical member 56 secured tothe hub 102.

Although the second air passage is constituted of the right axle-gap airpassage 52 formed in the hub 102 in the above first embodiment,modifications may be made as needed. For example, the second air passagemay be constituted of through holes formed through the supporting parts102 b and 102 c and extending from the partitioned space 111 to theoutside instead of or in conjunction with the right axle-gap air passage52. More specifically, the supporting parts 102 b and 102 c may berotatably supported on the hub 102 via sealed bearings, and throughholes formed through the radially outer parts of the sealed bearings forthe supporting parts 102 b and 102 c and extending from the partitionedspace 111 to the outside may be used as the second air passage.

Although the waterproof mechanism is constituted of the first airpassage 51, the second air passage 52, the third air passage 54 and theseal member 55 in the above first embodiment, the waterproof mechanismmay be constituted of a bore formed through the outer casing 3 b forcommunicating the air intake port 4 of the inner casing 3 b with theoutside and a film covering the bore which passes air therethrough butprevents passage of fluid so that only air can be allowed to pass andrainwater or the like can be prevented from entering the bore from theoutside of the outer casing 3 b by the film.

Although the taper angle P of the taper part 59 a of the cylindricalmember 56 is 10° in the above first embodiment, the taper angle is notlimited thereto and may be different as needed. Preferably, the taperangle P is in the range of approximately 5 to 15°. When the taper angleP is smaller than 5°, water cannot be smoothly moved toward thelarge-diameter side and discharged from the taper part 59 a by acentrifugal force created by the rotation of the hub. Also, water cannotbe smoothly moved toward the large-diameter side and discharged from thetaper part 59 a by its own weight. When the taper angle P is greaterthan 15°, falling rainwater or the like can easily enter the taper part59 a.

Although the widths L1 of the small-diameter small-width part 59 c andthe width L2 of the large-diameter small-width part 61 of the third airpassage 54 are both approximately 0.5 mm in the above first embodiment,the widths L1 and L2 may be different as needed. Preferably, the widthsL1 and L2 are in the range of approximately 0.1 to 1.5 mm. When thewidths L1 and L2 are smaller than approximately 0.1 mm, a negativepressure is created in the partitioned space 111 of the hub 102 andwater may be sucked into the partitioned chamber 111 together with airwhen the piton rod 33 is slid in the compression chamber 31 and air issucked into the compression chamber 31 from the partitioned space 111.When the widths L1 and L2 are greater than approximately 1.5 mm, watercan easily enter the partitioned space 111. As has been described above,the third air passage 54 is defined between the inner surface of thecylindrical member 56 secured to the hub 102 and the outer periphery ofthe axle 101 in this embodiment. Also, the third air passage 54 has thesmall-diameter small-width part 59 c with a small radial width L1 formedby partially reducing the inside diameter of the cylindrical member 56.In addition, the third air passage 54 has the large-diameter small-widthpart 61 defined by the cover member 60 located inside the cylindricalmember 56 and secured to the axle body 102 d, and having a radial widthL2 which is generally the same as that of the small-diameter small-widthpart 59 c and a diameter greater than that of the small-diametersmall-width part 59 c. As described above, the third air passage 54 hasat least two small-width parts 59 c and 61 which are different in atleast diameter so that air can flow windingly because of the twosmall-width parts 59 c and 61. The radial widths L1 and L2 of the twosmall-width parts 59 c and 61 are in the range of approximately 0.1 to1.5 mm.

Description will be next made of a second embodiment. FIG. 9 is a sideview of a wheel of a wheelchair provided with an automatic air-feedingmechanism for a pneumatic tire according to the second embodiment, andFIG. 10 is an enlarged cross-sectional explanatory view taken along theline X-X in FIG. 1.

The automatic air-feeding mechanism of the second embodiment is providedon both a left wheel 500 and a right wheel (not shown) of a wheelchairto constitute an automatic air-feeding mechanism for pneumatic tires ofa wheelchair. The left wheel 500 and the right wheel of the wheelchairprovided with the automatic air-feeding mechanism for pneumatic tires ofa wheelchair are the same in construction. Description will be made ofthe left wheel 500 and description of the right wheel will be omitted.

The left wheel 500 has an axle 101 and a wheel body 110. The axle 101 isthe same in construction as the axle 101 in the first embodiment.

As shown in FIG. 9, the wheel body 110 has a hub 102, a pneumatic tire103 and an automatic air-feeding mechanism. The hub 102 and thepneumatic tire 103 are the same in construction as the hub 102 and thepneumatic tire 103 in the first embodiment.

The automatic air-feeding mechanism has a plurality of compressed airproducing sections 1 a and 1 b, and pneumatic tire compressed air supplypassages 2 a and 2 b for introducing compressed air produced in thecompressed air producing sections 1 a and 1 b to the pneumatic tire.

In this embodiment, the compressed air producing sections are a firstcompressed air producing section 1 a shown on the upper part in FIG. 10and FIG. 11 and a second compressed air producing section 1 b shown onthe lower part in FIG. 10 and FIG. 11.

The first and second compressed air producing sections 1 a and 1 b arethe same in construction as the compressed air producing sections 1 ofthe first embodiment. The first and second compressed air producingsections 1 a and 1 b are spaced 180° apart from each other around thehub drum 102 a and secured to the outer periphery of a hub drum 102 a bybolts 30 c and 30 c.

The first and second compressed air producing sections 1 a and 1 b havepiston members 32 and 32, which are retained by a disk-shaped pistonretaining part 92 of a cam 9 via retention pins 36 and 36 attached tothe piston members 32 and 32 as in the case of the piston member 32 ofthe first embodiment.

In the second embodiment, the piston retaining part 92 of the cam 9 hasa retention body 89, a slider 80 slidable along the retention body 89,and a supporting member 90 for slidably supporting the slider 80 asshown in FIG. 13A and FIG. 13B.

The slider 80 has a cylindrical shape as shown in FIG. 12A and FIG. 12B.The inner periphery of the slider 80 defines a retention pin insertionhole 83 for receiving the retention pin 36. The slider 80 has acylindrical part 81 and a flange 82 with a diameter larger than that ofthe cylindrical part 81 on the outer periphery thereof.

The retention body 89 has a first pin insertion hole 92 b and a secondpin insertion hole 95 formed on a circle 96 about the axis of the cambody receiving hole 92 a, which coincides with the center O1 of the camface 91 a, as shown in FIG. 13A and FIG. 13B.

The first pin insertion hole 92 b is a circular hole as in the case ofthe pin insertion hole 92 b of the first embodiment. The retention pin36 of the piston member 32 of the first compressed air producing section1 a is rotatably inserted in the first pin insertion hole 92 b.

The second pin insertion hole 95 has a sliding groove 95 a as an arcuateslit with a specific length in the circumferential direction of thecircle 96 and a seat part 95 b formed around the sliding groove 95 a andextending to a specific width and a specific length from the left sideof the piston retaining part 92.

The cylindrical part 81 of the slider 80 is received in the slidinggroove 95 a of the second pin insertion hole 95, and the slider 80 isslidably received in the second pin insertion hole 95 with the flange 82in contact with the seat part 95 b.

The slider 80 received in the second pin insertion hole 95 as describedabove is movable in the second pin insertion hole 95 between a startposition 97 a where the cylindrical part 81 abuts against a first end 95c of the sliding groove 95 a and an end position 97 b where thecylindrical part 81 abuts against a second end 95 d of the slidinggroove 95 a.

The position of the second pin insertion hole 95 receiving the slider 80as described above with respect to the first pin insertion hole 92 b andthe length of the sliding groove 95 a of the second pin insertion hole95 is determined as follows in this embodiment.

A line extended from the axis 92 d of the first pin insertion hole 92 bthrough the center O1 of the cam face 91 a until it crosses to thecircle 96 as shown in FIG. 13B is defined as a reference line 98. Thesecond pin insertion hole 95 is formed such that the axis 83 a of theretention pin insertion hole 83 of the slider 80 is rotatable from theintersection of the reference line 98 and the circle 96 in bothclockwise and counterclockwise directions through angles Ψ/2 and Ψ/2 ofapproximately 36° about the center O1 of the cam face 91 a to the startposition 97 a and the end position 97 b of the slider 80.

The supporting member 90 functions as slider inclination preventingmeans for preventing the slider 80 from being inclined with respect tothe axial direction of the axle 101 when it is slid and has a disk-likeshape as shown in FIG. 13A. The supporting member 90 covers the slider80 received in the second pin insertion hole 95 from the side of theseat part 95 b thereof and attached to the axle 101. The flange 82 ofthe slider 80 is thereby kept in contact with the seat part 95 b whenthe slider 80 is slid in the second pin insertion hole 95. Thus, theaxis of the retention pin insertion hole 83 of the slider 80 can be keptin generally parallel to the axis of the axle 101 and is not inclinedwith respect to the axial direction of the axle 101 when the slider 80is slid in the second pin insertion hole 95.

The retention pin 36 of the piston member 32 of the second compressedair producing section 1 b is inserted in the retention pin insertionhole 83 of the slider 80 received in the second pin insertion hole 95 asdescribed above. The retention pin 36 is thereby movable, together withthe slider 80, in the second pin insertion hole 95 in thecircumferential direction of the cam face 91 a through an angle Ψ ofapproximately 72° about the center O1 of the cam face 91 a.

Since the first and second compressed air producing sections 1 a and 1 bare positioned as described above, when the roller 37 of the pistonmember 32 of the first compressed air producing section 1 a is incontact with the small-diameter point A of the cam face 91 a and thesliding part 34 of the piston rod 33 is in the lowermost position A1 inthe compression chamber 31 in the first compressed air producing sectionla, the retention pin 36 of the piston member 32 of the secondcompressed air producing section 1 b is located generally in the middleof the second pin insertion hole 95, the roller 37 of the piston member32 of the second compressed air producing section 1 b is in contact withthe large-diameter point B of the cam face 91 a, and the sliding part 34of the piston rod 33 is in the uppermost position B1 in the compressionchamber 31 in the second compressed air producing section 1 b as shownin FIG. 10 and FIG. 11.

The pneumatic tire compressed air supply passages 2 a and 2 b will benext described. The pneumatic tire compressed air supply passages of thesecond embodiment are constituted of the first pneumatic tire compressedair supply passage 2 a formed between the first compressed air producingsection 1 a and the pneumatic tire 103 and the second pneumatic tirecompressed air supply passage 2 b formed between the second compressedair producing section 1 b and the pneumatic tire 103.

The first pneumatic tire compressed air supply passage 2 a, which is thesame in construction as the pneumatic tire compressed air supply passage2 of the first embodiment, has a communication supply passage 13 bcommunicated with the compression chamber 31 of the first compressed airproducing section la, a pneumatic tire feeding supply passage 13 a, anda connection supply passage 21 a connecting the communication supplypassage 13 b and the pneumatic tire feeding supply passage 13 a.

The second pneumatic tire compressed air supply passage 2 b has, as inthe case of the first pneumatic tire compressed air supply passage 2 a,a communication supply passage 13 b, a pneumatic tire feeding supplypassage, and a connection supply passage. The communication supplypassage 13 b of the second pneumatic tire compressed air supply passage2 b is, however, connected to the connection supply passage 21 a of thefirst pneumatic tire compressed air supply passage 2 a via a connectionpassage 22 a. That is, the second pneumatic tire compressed air supplypassage 2 b is connected to the pneumatic tire feeding supply passage 13a of the first pneumatic tire compressed air supply passage 2 a and thepneumatic tire 103 via the connection supply passage 21 a. Thus, in thisembodiment, the connection supply passage 21 a and the pneumatic tirefeeding supply passage 13 a of the first pneumatic tire compressed airsupply passage 2 a serve also as the connection supply passage and thepneumatic tire feeding supply passage, respectively, of the secondpneumatic tire compressed air supply passage 2 b.

The operation of the automatic air-feeding mechanism for a pneumatictire of a wheelchair according to the second embodiment will bedescribed. The pneumatic tire 103 is rotated about the axle 101 from thestate in which the sliding part 34 is in the lowermost position A1 inthe compression chamber 31 in the first compressed air producing section1 a and the sliding part 34 is in the uppermost position B1 in thecompression chamber 31 in the second compressed air producing section 1b as shown in FIG. 10 and FIG. 11, by, for example, pushing thewheelchair. Then, the hub 102 is rotated, and the roller 37 of thepiston member 32 of the first compressed air producing section 1 a runson the cam face 91 a of the cam 9 from the small-diameter point A towardthe large-diameter point B and the roller 37 of the piston member 32 ofthe second compressed air producing section 1 b runs on the cam face 91a of the cam 9 from the large-diameter point B toward the small-diameterpoint A.

At this time, the retention pin 36 of the piston member 32 of the secondcompressed air producing section 1 b is moved together with the slider80 in the second pin insertion hole 95 toward the first end 95 c ofsliding groove 95 a of the second pin insertion hole 95 until the slider80 reaches the start position 97 a and the cylindrical part 81 abutsagainst the first end 95 c as shown in FIG. 14.

If the retention pin 36 is directly received in the second pin insertionhole 95 so that it can be slid in the second pin insertion hole 95without the slider 80 and if the piston member 32 is rotatably receivedin the compression chamber 31 in the second compressed air producingsection 1 b, when a resistance is applied to the retention pin 36 whenit is sliding in the second pin insertion hole 95, the retention pin 36may not be slid further in the second pin insertion hole 95 and thepiston member 32 may be rotated via the retention pin 36 in thecompression chamber 31 to incline the axial direction of the retentionpin 36 with respect to the axial direction of the axle 101. When theaxial direction of the retention pin 36 is inclined with respect to theaxial direction of the axle 101, the axis of the roller 37 running onthe cam face 91 a of the cam 9 may be inclined to the extent that theroller 37 cannot run on the cam face smoothly or the retention pin 36may get out of the second pin insertion hole 95. Then, the piston member32 cannot be slid in the compression chamber 31 smoothly.

In this embodiment, however, since the retention pin 36 is movedtogether with the slider 80 slidable in the second pin insertion hole95, the retention pin 36 can be smoothly slid in the second pininsertion hole 95. Thus, even if the piston member 32 is rotatablyreceived in the compression chamber 31 in the second compressed airproducing section 1 b, the retention pin 36 can be smoothly slid in thesecond pin insertion hole 95 together with the slider 80, and the pistonmember 32 can be slid in the compression chamber 31 smoothly.

When the roller 37 runs further, the piston member 32 of the firstcompressed air producing section 1 a is pressed by the cam 9 and keptpressed until the roller 37 of the piston member 32 reaches thelarge-diameter point B of the cam 9. At this time, the sliding part 34is slid in the compression chamber 31 along the inner wall thereof fromthe lowermost position A1 to the uppermost position B1 as shown in FIG.15 and FIG. 16.

While the sliding part 34 is slid from the lowermost position A1 to theuppermost position B1, the air in the compression chamber 31 iscompressed up to a certain compression ratio.

The compressed air produced in the first compressed air producingsection 1 a is, as in the case of the first embodiment, is fed from thecommunication supply passage 13 b to the connection supply passage 21 aand introduced from the connection supply passage 21 a through thepneumatic tire feeding supply passage 13 a into the pneumatic tire 103as needed.

At the same time, the retention pin 36 of the piston member 32 of thesecond compressed air producing section 1 b is moved together with theslider 80 from the start position 97 a shown in FIG. 14 to almost themiddle of the sliding groove 95 a of the second pin insertion hole 95 asshown in FIG. 16. When the retention pin 36 is moved as described above,the sliding part 34 of the piston rod 33 of the second compressed airproducing section 1 b is pulled by the cam 9 to slide in the compressionchamber 31 along the inner wall thereof from the uppermost position B1toward the lowermost position A1.

The roller 37 of the piston member 32 of the second compressed airproducing section 1 b reaches the small-diameter point A of the cam face91 a and the sliding part 34 of the piston rod 33 reaches the lowermostposition A1 in the second compressed air producing section 1 b when theroller 37 of the piston member 32 of the first compressed air producingsection 1 a reaches the large-diameter point B of the cam face 91 a asshown in FIG. 15 and FIG. 16.

When the sliding part 34 of the piston rod 33 of the second compressedair producing section 1 b is moved from the uppermost position B1 to thelowermost position A1, the cam 9 pulls left side of the piston rod 33 ofthe piston member 32, which is at a distance from the extension q of theaxis of the piston rod 33, since the retention pin 36 of the pistonmember 32 is retained by the piston retaining part 92 of the cam 9.However, when the sliding part 34 is slid from the uppermost position B1to the lowermost position A1, the sliding part 34 can be slid by a forcesmaller than that required when the sliding part 34 is slid from thelowermost position A1 to the uppermost position B1 to compress air sincecompression of air is not conducted and hence the piton rod 33 can bepulled smoothly.

When the sliding part 34 of the piston rod 33 passes the air intake port4 in the second compressed air producing section 1 b, air is introducedfrom the partitioned space 111 of the hub 102 into the compressionchamber 31 through the first air passage 51 and the air intake port 4.Since the second air passage 52 and the third air passage 54 preventwater from entering the partitioned space 111 of the hub 102, only aircan enter the partitioned space 111.

When the hub 102 is further rotated from the state shown in FIG. 16, thepiston member 32 of the first compressed air producing section 1 a ispulled by the cam 9 via the retention pin 36 and the roller 37 runs onthe cam face 91 a from the large-diameter point B toward thesmall-diameter point A as shown in FIG. 17. The sliding part 34 isthereby moved from the uppermost position B1 toward the lowermostposition A1 in the first compressed air producing section 1 a (see FIG.11).

The retention pin 36 of the piston member 32 of the second compressedair producing section 1 b is moved together with the slider 80 in thesecond pin insertion hole 95 toward the second end 95 d of the slidinggroove 95 a until the slider reaches the end position 97 b and thecylindrical part 81 abuts against the second end 95 d. At this time, theroller 37 of the piston member 32 runs on the cam face 91 a from thesmall-diameter point A to the large-diameter point B and the roller 37of the piston member 32 is pressed by the cam face 91. Then, the slidingpart 34 is moved in the compression chamber 31 from the lowermostposition A1 to the uppermost position B1 (see FIG. 11). By the movementof the sliding part 34, the air in the compression chamber 31 iscompressed up to a certain compression ratio.

The compressed air produced in the second compressed air producingsection 1 b is fed into the connection supply passage 21 a of the firstpneumatic tire compressed air supply passage 2 a through the pneumatictire feeding supply passage 13 b of the second pneumatic tire compressedair supply passage 2 b and the connection passage 22 a. The compressedair fed into the connection supply passage 21 a of the first compressedair passage 1 b is introduced into the pneumatic tire 103 through thepneumatic tire feeding supply passage 13 a as in the case of thecompressed air from the first compressed air producing section 1 a.

After that, when the hub 102 is rotated, the first compressed airproducing section 1 a and the second compressed air producing section 1b alternately produce compressed air and supply the compressed air intothe pneumatic tire 103 as needed.

As described above, whenever the wheel body is rotated, the first andsecond compressed air producing section 1 a and 1 b can alternatelyproduce compressed air and supply the compressed air into the pneumatictire 103. Thus, compressed air can be produced with almost the sameforce as that required to produce compressed air with one compressed airproducing section 1 as in the first embodiment, and compressed air canbe produced in an amount twice the amount of compressed air which can beproduced by one compressed air producing section 1 as in the firstembodiment. Therefore, when the wheelchair is driven normally, asufficient amount of air to increase the air pressure in the pneumatictire 103 to a required level can be compressed within a short period oftime after the start of running even if the number of rotations of thewheel is still low. In addition, the resistance to the travel of thewheelchair is not increased. Thus, this embodiment is suitable for awheelchair.

Although the first and second pneumatic tire compressed air supplypassages 2 a and 2 b are connected via the connection passage 22 a inthe second embodiment, the first and second pneumatic tire compressedair supply passages 2 a and 2 b may be separately formed and connectedto the pneumatic tire 103 so that compressed air can be supplied to thepneumatic tire 103 separately through the first and second pneumatictire compressed air supply passages 2 a and 2 b.

Description will be next made of an automatic air-feeding mechanismaccording to a third embodiment with reference to FIG. 18 to FIG. 22.The automatic air-feeding mechanism according to the third embodiment isprovided on a bicycle for supplying air to a pneumatic tire on a wheeland for supplying air to a saddle as a part of the bicycle other thanthe pneumatic tire to provide the seat with good cushion.

The automatic air-feeding mechanism according to the third embodimenthas two compressed air producing sections, that is, first and secondcompressed air producing section 10 a and 10 b as in the case of theautomatic air-feeding mechanism according to the second embodiment, andcompressed air supply passages 20 a and 300.

The first and second compressed air producing sections 10 a and 10 b,which are the same in construction as the compressed air producingsection of the first embodiment, are attached to a front wheel 202 of abicycle. The front wheel 202 of the bicycle has, as in the case of thewheel of a bicycle in the first embodiment, an axle 201 and a wheel bodyhaving a hub 102 rotatably supported by the axle 201 and a pneumatictire 103 as shown in FIG. 18.

In the third embodiment, the axle 201 has an axial hole 43 a as shown inFIG. 19. The axial hole 43 a extends in the axle 201 along the axisthereof from the left end to a point slightly on the left of the centerthereof. That is, the axial hole 43 a extends from the outside of thehub 102 attached to the axle 201 to the inside thereof. The bottom ofthe axial hole 43 a extended into the hub 202 is communicated with theoutside of the axle 201 via through holes 43 b and 43 b extending fromthe axial hole 43 a to the outer periphery of the axle 201 as shown inFIG. 21.

The hub 102 of the wheel body and the pneumatic tire 103 are generallythe same in construction as the hub 102 and the pneumatic tire 103 ofthe first embodiment.

The automatic air-feeding mechanism has a pneumatic tire compressed airsupply passage 20 a for introducing compressed air produced in the firstcompressed air producing section 10 a to the pneumatic tire 103 and ananother part compressed air supply passage 300 for introducingcompressed air produced in the second compressed air producing section10 b to a saddle 140 of the bicycle. The pneumatic tire compressed airsupply passage 20 a is the same in construction as the pneumatic tirecompressed air supply passage 2 of the first embodiment.

The another part compressed air supply passage 300 has a communicationsupply passage 13 b (shown in FIG. 19) communicated with the compressionchamber 31 of the second compressed air producing section 10 b, a saddlefeeding supply passage 301 connected to an air holding part 151 (shownin FIG. 22) of the saddle 140 of the bicycle, and a connection supplypassage 302 connecting the communication supply passage 13 b and thesaddle feeding supply passage 301.

The connection supply passage 302 has the axial hole 43 a in the axle201 and a connection passage 303 connecting the axial hole 43 a and thecommunication supply passage 13 b as shown in FIG. 19. The connectionpassage 303 is defined in a connection pipe 313. The connection pipe 313is connected to the axial hole 43 a in the axle 201 via a rotaryconnection member 45.

The rotary connection member 45 has two rings 45 a and 45 a made of asynthetic rubber and a ring-shaped rotor 45 b as shown in FIG. 20 andFIG. 21.

The two rings 45 a and 45 a are fixed to the outer periphery of the axle201 on both sides of the through holes 43 b and 43 b.

The rotor 45 b has a pipe coupler 45 c to which the connection pipe 313can be removably connected on its outer periphery. The pipe coupler 45 chas a cylindrical shape and defines a pipe connection hole 45 dtherethrough.

An air reserving part 45 e is circumferentially formed in the innersurface of the rotor 45 b as shown in FIG. 20. The air reserving part 45e is communicated with the pipe connection hole 45 d of the pipe coupler45 c via a bore 45 f extending from the pipe connection hole 45 d to theair reserving part 45 e. The air reserving part 45 e, the pipeconnection hole 45 d and the bore 45 f constitutes a connection hole 45i for connecting the connection passage 303 of the connection pipe 313in air flow communication with the axial hole 43 a.

The rotor 45 b has ring receiving parts 45 g and 45 g for rotatablyreceiving the rings 45 a and 45 a on both right and left sides of theair reserving part 45 e. The rings 45 a and 45 a are rotatably receivedin the ring receiving parts 45 g and 45 g , and the rotor 45 b isthereby rotatable about the axle 201 with the air reserving part 45 ecommunicated with the axial hole 43 a in the axle 201.

The connection pipe 313 is connected to the pipe coupler 45 c of therotor 45 b constituted as described above, whereby the connection pipe313 and the axle 201 are rotatably connected via the rotor 45 b. By theconnection, the connection passage 303 formed in the connection pipe 313and the axial hole 43 a formed in the axle 201 of the wheel 202 iscommunicated with each other.

The connection pipe 313 is attached to the inner casing 3 a via acoupler 314 as shown in FIG. 19, whereby the connection passage 303formed in the connection pipe 313 is connected in air flow communicationwith the communication supply passage 13 b defined in the inner casing 3a by the partition 7.

The coupler 314 has a pressure adjusting section for controlling the airpressure in the another part compressed air supply passage 300, althoughnot shown. The pressure adjusting section is the same in construction asthe pressure adjusting section 12 of the first embodiment.

The saddle feeding supply passage 301 of the another part compressed airsupply passage 300 is formed in a pipe member 310. The proximal end ofthe pipe member 310 defining the saddle feeding supply passage 301therein is connected to the axle 201 of the wheel 202 via a coupler 310a. The saddle feeding supply passage 301 is thereby connected in airflow communication with the axial hole 43 a in the axle 201.

The distal end of the pipe member 310 is connected to the saddle 140 ofthe bicycle.

In this embodiment, the saddle 140, to which the pipe member 310 isconnected, has a seat 141 for the rider to sit on and a seat supportingpart 142 for supporting the seat 141 as shown in FIG. 22. The seatsupporting part 142 has a seat supporting piece 143 for supporting theseat 141 and a seat mounting part 150 to which the seat supporting piece143 is attached for vertical movement.

The seat mounting part 150 has an air holding part 151 for holding airtherein. The air holding part 151 has an air inlet 152 through which airis fed in and ejected. The pipe member 310 is connected to the air inlet152. The saddle feeding supply passage 301 is thereby connected in airflow communication with the air holding part 151.

A lower part of the seat mounting part 150 is inserted into and securedto a vertical pipe 210 of the bicycle. The seat mounting part 150 is notnecessarily formed separately from the vertical pipe 210 and may beformed as a part of the vertical pipe 210.

An upper part of the seat supporting piece 143 is secured to the seat141. The seat supporting piece 143 has an air pressing part 144 forpressing the air in the air holding part 151 downward at its lower end.The air pressing part 144 is disposed in the air holding part 151 of theseat mounting part 150 and vertically slidable along the inner wall ofthe air holding part 151.

In this embodiment, a coil spring 153 as a pressing part urging memberfor urging the air pressing part 144 upward is disposed in the airholding part 151 as shown in FIG. 22 so that it can assist the airpressing part 144 having been slid down in the air holding part 151 tobe returned upward by the pressure of compressed air.

When a person sits on the seat 141 constituted as described above and adownward force is applied to the air pressing part 144, the air pressingpart 144 is moved downward together with the seat 141 and compresses theair in the air holding part 151.

When the force applied to the air pressing part 144 is reduced, the seat141 is returned upward by the pressure of compressed air in the airholding part 151. The seat 141 can thereby have good cushion and canabsorb shocks on the seat 141 to ensure a comfortable ride.

The operation of the automatic air-feeding mechanism for a bicycleaccording to the third embodiment will be described.

The wheel body is rotated about the axle 201 from the state in which thesliding part 34 is in the lowermost position A1 in the compressionchamber 31 in the first compressed air producing section 10 a and thesliding part 34 is in the uppermost position B1 in the compressionchamber 31 in the second compressed air producing section 10 b as shownin FIG. 19 by, for example, riding the bicycle. Then, the hub 102 isrotated, and the roller 37 of the piston member 32 of the firstcompressed air producing section 10 a runs on the cam face 91 a of thecam 9 and the roller 37 of the piston member 32 of the second compressedair producing section 1 b runs on the cam face 91 of the cam 9.

At this time, the sliding part 34 of the piston rod 33 is slid in thecompression chamber 31 from the lowermost position A1 to the uppermostposition B1 in the first compressed air producing section 10 a, as inthe first compressed air producing section la of the first embodiment,and the air in the compression chamber 31 is compressed up to a certaincompression ratio. The compressed air is fed into air tube 103 b of thepneumatic tire 103 through the pneumatic tire compressed air supplypassage 20 a as needed. When the roller 37 runs further, the slidingpart 34 of the piston rod 33 is slid in the compression chamber 31 fromthe uppermost position B1 toward the lowermost position A1. Then, whenthe sliding part 34 passes the air intake port 4, air is introduced intothe compression chamber 31. At this time, air is introduced from thepartitioned space 111 of the hub 102 into the compression chamber 31through the first air passage 51 and the air intake port 4. Also, air isintroduced into the partitioned space 111 from the outside of the hub102 through the second and third air passages 52 and 54. Thus, also inthe third embodiment, rainwater or the like can be prevented fromentering the compression chamber 31.

In the second compressed air producing section 10 b, the sliding part 34of the piston rod 33 is slid in the compression chamber 31 from theuppermost position B1 to the lowermost position Al when the sliding part34 of the piston rod 33 of the first compressed air producing section 10a is slid from the lowermost position A1 to the uppermost position B1.When the sliding part 34 passes the air intake port 4, air is introducedinto the compression chamber 31. Also at this time, rainwater or thelike can be prevented from entering the compression chamber 31.

When the sliding part 34 of the piston rod 33 is slid in the compressionchamber 31 from the uppermost position B1 to the lowermost position A1in the first compressed air producing section 10 a, the sliding part 34of the piston rod 33 is slid in the compression chamber 31 from thelowermost position A1 to the uppermost position B1 to compress the airin the compression chamber 31 up to a certain compression ratio in thesecond compressed air producing section 10 b.

The air compressed in the second compressed air producing section 10 bis fed from the compression chamber 31 to the communication supplypassage 13 b and then fed from the communication supply passage 13 b tothe saddle feeding supply passage 301 through the connection passage 303and the axial hole 43 a in the axle 201. The compressed air is then fedfrom the saddle feeding supply passage 301 to the air holding part 151of the saddle 140. Since the connection passage 303 and the axial hole43 a are rotatably connected via the connection hole 45 i of the rotaryconnection member 45, the connection passage 303 and the axial hole 43 aare kept communicated with each other even when the bicycle runs and thewheel body is rotated. Thus, when the bicycle is ridden, compressed airis produced in the second compressed air producing section 10 b and theproduced compressed air can be fed from the wheel 202 to the saddle 140of the bicycle.

The interior of the air holding part 151 can be thereby maintained atthe same air pressure as in the another part compressed air supplypassage 300, and, when the air pressure in the air holding part 151becomes lower than a predetermined level, compressed air can besequentially produced in the second compressed air producing section 10b and introduced into the air holding part 151 as long as the bicycle isrunning.

Although the air pressing part 144 presses the air holding part 151 tocompress the air in the air holding part 151 in the third embodiment,the present invention is not limited thereto and may be modified asneeded. For example, the air holding part 151 may be provided as a partof the seat 141 so that, when the rider sits on the seat 141, the airholding part 151 can receive the load and provide the seat 141 with goodcushion.

When the seat pressing part 144 is provided, the air holding part 151and the air pressing part 144 are not necessarily provided in the seatmounting part 150 and in the saddle 140, respectively, as in the aboveembodiment and modifications may be made as needed. For example, the airholding part 151 and the air pressing part 144 may be provided in theseat supporting piece 143 and the seat mounting part 150, respectively.

A check valve may be provide in the air holding part 151 to prevent airfrom flowing in reverse from the air holding part 151 to the saddlefeeding supply passage 301.

Although the automatic air-feeding mechanism is provided on the frontwheel 202 in the third embodiment, modifications may be made as needed.For example, the automatic air-feeding mechanism may be may be providedon the rear wheel.

Description will be next made of an automatic air-feeding mechanismaccording to a fourth embodiment with reference to FIG. 23 to FIG. 25.The automatic air-feeding mechanism according to the fourth embodimentis provided on a bicycle as a vehicle for supplying air to a pneumatictire on a wheel and for supplying air to a brake device as a part of thebicycle other than the pneumatic tire to prevent overheating of thebrake device.

The automatic air-feeding mechanism according to the fourth embodimenthas, as in the case of the automatic air-feeding mechanism according tothe third embodiment, two compressed air producing sections, that is,first and second compressed air producing sections 400 a and 400 b, andcompressed air supply passages 200 a and 400.

The first and second compressed air producing sections 400 a and 400 bare attached to the rear wheel of the bicycle as a vehicle. The axle 201of the rear wheel and the pneumatic tire (not shown) on the wheel bodyare generally the same in construction as the axle 201 and the pneumatictire 103 of the third embodiment.

Each of the first and second compressed air producing sections 400 a and400 b has a first air passage 51 communicating an air intake port 4 witha partitioned space 111 of a hub 402 of the rear wheel, and a second airpassage extending from the first air passage 51. In the fourthembodiment, however, the right side of the right axle-gap air passage 52of the hub 402 of the rear wheel is generally sealed from the outside bya ring-shaped seal member 550, and the left axle-gap air passage 53 ofthe hub 402 of the rear wheel constitutes the second air passage so thatoutside air can be introduced into the partitioned space 111 through theleft axle-gap air passage 53.

Except that, the first and second compressed air producing sections 400a and 400 b are the same in construction as the first compressed airproducing sections 10 a of the third embodiment.

In the fourth embodiment, the automatic air-feeding mechanism has apneumatic tire compressed air supply passage 200 a for introducingcompressed air produced in the first compressed air producing section400 a to the pneumatic tire 103 and an another part compressed airsupply passage 400 for introducing compressed air produced in the secondcompressed air producing section 400 b to a brake device of the bicycle.The pneumatic tire compressed air supply passage 200 a is the same inconstruction as the pneumatic tire compressed air supply passage 2 ofthe first embodiment.

In the fourth embodiment, the another part compressed air supply passage400 has a communication supply passage 13 b communicated with thecompression chamber 31 of the second compressed air producing section400 b, a brake feeding supply passage 401 connected to a hereinafterdescribed brake device 120 of the bicycle, and a connection supplypassage 402 connecting the communication supply passage 13 b and thebrake feeding supply passage 401. The communication supply passage 13 bis the same in construction as the communication supply passage 13 b ofthe third embodiment.

The connection supply passage 402 of the another part compressed airsupply passage 400 is the same in construction as the connection supplypassage 302 of the third embodiment. More specifically, the connectionsupply passage 402 of the another part compressed air supply passage 400has an axial hole 43 a formed in the axle 201 and a connection passage403 connecting the axial hole 43 a and the communication supply passage13 b. The connection passage 403 is defined in a connection pipe 413.The connection pipe 413 is rotatably connected to the axle 201 via arotary connection member 45, whereby the connection passage 403 of theconnection pipe 413 is rotatably connected in air flow communicationwith the axial hole 43 a in the axle 201.

The brake feeding supply passage 401 is defined in a pipe member 410.The proximal end of the pipe member 410 is connected to the axle 201 ofthe rear wheel via a coupler 410 a. The brake feeding supply passage 401is thereby connected in air communication with the axial hole 43 a inthe axle 201.

The distal end of the pipe member 410 is connected to the brake device120 for the rear wheel of the bicycle.

The brake device 120 for the rear wheel will be described briefly. Thebrake device 120 is an internal expanding brake 120 in this embodiment.The internal expanding brake 120 has a drum 121 as a member to bebraked, a brake shoe 122 as a braking member, and a cover 123 forcovering the drum 121 and the brake shoe 122 as shown in FIG. 23.

The drum 121 has a cylindrical part 121 a, and a lining contact part 121b inside the cylindrical part 121 a. The drum 121 is attached to a drumattaching screw 405 a of the hub 402 of the rear wheel and therebysecured to the hub 402 of the rear wheel. The lining contact part 121 bis thereby rotatable together with the hub 402 of the rear wheel.

The cover 123 has a disk part 123 a and a cylindrical part 123 bextending from the peripheral edge of the disk part 123 a. A pipeconnection port 123 c is formed through the cylindrical part 123 b, andthe brake feeding supply passage 401 is connected to the pipe connectionport 123 c. The axle 201 extends through the cover 123, and the cover123 is fixed to the axle 201 by a cover fixing nut 123 d. The drum 121is thereby covered with the cylindrical part 123 b of the cover 123 fromthe outer peripheral side thereof.

The brake shoe 122 has a pair of shoe pieces 122 a and 122 a with anarcuate shape as shown in FIG. 24. The shoe pieces 122 a and 122 a havelinings 122 b and 122 b made of a synthetic rubber on their outer side.The shoe pieces 122 a and 122 a are located inside the drum 121 androtatably supported on the cover 123 by a fixing bolt 122 c extendingthrough the proximal ends of the shoe pieces 122 a and 122 a. The distalends of the shoe pieces 122 a and 122 a are thereby rotatable abouttheir proximal ends. A shoe operating cam 124 for rotating the shoepieces 122 a and 122 a is located between the distal ends of the shoepieces 122 a and 122 a.

The shoe operating cam 124 has a small-diameter part 124 a and alarge-diameter part 124 b with a diameter larger than that of thesmall-diameter part 124 a. The shoe operating cam 124 is connected to anarm member 125 for moving the shoe operating cam 124, and attached tothe cover 123 for rotation together with the arm member 125.

The arm member 125 is connected to a brake lever (not shown) via a brakewire 133. When the brake lever is operated, the arm member 125 is movedto rotate the shoe operating cam 124 as shown in FIG. 25.

When the shoe operating cam 124 is rotated, the large-diameter part 124b of the shoe operating cam 124 presses the distal ends of the shoepieces 122 a and 122 a. Then, the linings 122 b and 122 b of the shoepieces 122 a and 122 a are pressed against the lining contact part 121 bof the drum 121 to stop the rotation of the drum 121.

When the brake lever is released, the shoe pieces 122 a and 122 a arereturned to the original positions by the urging force of a coil spring126 connecting the shoe pieces 122 a and 122 a, and the linings 122 band 122 b are separated from the lining contact part 121 b of the drum121.

The distal end of the pipe member 410 is connected to the pipeconnection port 123 c of the cover 123 of the internal expanding brake120 constituted as describe above.

The operation of the automatic air-feeding mechanism for a bicycleaccording to the fourth embodiment will be described.

The wheel body is rotated about the axle 201 also in the fourthembodiment as in the case of the third embodiment by, for example,riding the bicycle. Then, the first and second compressed air producingsections 400 a and 400 b alternately compress air. The air compressed inthe first compressed air producing section 400 a is introduced into theair tube of the pneumatic tire through the pneumatic tire feeding supplypassage 200 a as needed.

The air compressed in the second compressed air producing section 400 bis fed to the brake feeding supply passage 401 through the communicationsupply passage 13 b, the connection passage 403 and the axial hole 43 ain the axle 201. Then, the compressed air reaches the pipe connectionport 123 c of the brake device 120 through the brake feeding supplypassage 401 and is blown from the pipe connection port 123 c onto thedrum 121. Air can be thereby constantly blown onto the drum 121 toreduce generation of heat caused by friction between the drum 121 andthe linings 122 b and 122 b when the bicycle is ridden. Even if thebrake device 120 is heated by direct sunlight in summer days, forexample, the brake device 120 can be cooled when the bicycle is ridden.Thus, problems caused by overheating of the brake device 120 can beavoided.

The automatic air-feeding mechanisms constituted as described aboveaccording to the above embodiments of the present invention can beunderstood as follows.

An automatic air-feeding mechanism according to one embodiment has aplurality of compressed air producing sections which produce compressedair when the wheel body is rotated about the axle, each one of thecompressed air producing sections having a compression chamber forcompressing air therein, an air intake port for introducing outside airinto the compression chamber, and a waterproof mechanism for preventingwater from entering the compression chamber through the air intake port.

The automatic air-feeding mechanism of the embodiment also has apneumatic tire compressed air supply passage for supplying thecompressed air produced in a compressed air producing section to apneumatic tire, and an another part compressed air supply passage forsupplying the compressed air produced in a compressed air producingsection to a part other than the pneumatic tire. The another partcompressed air supply passage is used to supply the compressed airproduced in the compressed air producing section to a brake device ofthe bicycle.

The brake device has a member to be braked rotatable together with apneumatic tire and a braking member movable into contact with the memberto be braked to stop the rotation of the member to be braked.

Alternatively, the another part compressed air supply passage is used tosupply the compressed air produced in a compressed air producing sectionto the saddle of the bicycle.

The saddle has a seat for the rider to sit on, and an air holding partcontaining air for receiving a load on the seat to provide the seat withgood cushion.

The saddle also has a seat supporting part for supporting the seat forvertical movement. The air holding part is formed in the seat supportingpart, which has an air pressing part which can press the air in the airholding part. When a downward load is applied to the seat, the airpressing part presses the air in the air holding part. Then, the air inthe air holding part is compressed and the seat is moved downward toprovide the seat with good cushion.

The another part compressed air supply passage has a communicationsupply passage communicated with the compression chamber of thecompressed air producing section and an another part feeding supplypassage connected to the saddle or brake device of the bicycle asanother part, and a connection supply passage connecting thecommunication supply passage and the another part feeding supplypassage. The connection supply passage has an axial hole formed axiallyin the axle and connected to the another part feeding supply passage,and a connection passage connecting the axial hole and the communicationsupply passage. The connection passage and the axial hole are rotatablyconnected via a connection hole rotatably connected to the axial hole.

The compressed air produced in the compressed air producing section,which is rotated together with the wheel body when the bicycle isrunning, can be thereby fed from the connection passage to theconnection supply passage via the axial hole and then from theconnection supply passage to another part of the bicycle such as thesaddle or brake device.

An automatic air-feeding mechanism according to one embodiment has nnumber of compressed air producing sections (n is an integer greaterthan 1), each of which has a compression chamber, and a compressingelement for compressing the air in the compression chamber. Each of thecompressing elements has a first end slidably received in thecompression chamber and a second end retained by a cam mounted on theaxle. When the wheel body is rotated about the axle, the compressingelements follow the cam and are slid in the compression chambers tocompress the air in the compression chambers. The cam has a cam bodyhaving a cam face in contact with the compressing elements on its outerperiphery, and an operation element retaining part located on one sideof the cam face of the cam body for rotation with respect to the cambody, and the second ends of at least (n-1) number of the compressingelements are retained by the operation element retaining part formovement in the circumferential direction of the operation elementretaining part.

The compressing elements can be thereby rotated about the axis of theaxle with the second ends thereof retained by the operation elementretaining part and kept in contact with the cam face of the cam. Thus,since the second ends of all the compressing elements can be retained byone operation element retaining part, the automatic air-feedingmechanism can be simple in construction and hence can be produced at lowcosts.

The operation element retaining part has a retention body, slidersattached to the retention body for sliding movement in thecircumferential direction of the retention body, and slider inclinationpreventing means for preventing the sliders from being inclined withrespect to the axial direction of the retention body when they are slid.The sliders retain the second ends of the compressing elements so thatthe compressing elements can be slid in the circumferential direction ofthe cam face 91 a together with the sliders.

Retention pins, for example, attached to the compressing elements can bethereby moved together with the sliders in the circumferential directionof the retention body. If the retention pins are directly received inpin insertion holes without the sliders and if the piston members arerotatably received in the compression chambers, when a resistance isapplied to the retention pins when they are being slid in the pininsertion holes, the retention pins cannot be slid further and thepiston members may be rotated in the compression chambers to incline theaxial direction of the retention pins with respect to the axialdirection of the axle. When the axial directions of the retention pinsare inclined with respect to the axial direction of the axle, the axisof rollers running on the cam face of the cam may be inclined to theextent that the rollers cannot run on the cam face smoothly or theretention pins may get out of the pin insertion holes. Then, the pistonmembers cannot be slid in the compression chambers smoothly. However,when the retention pins are moved together with the sliders in thecircumferential direction of the retention body as in this embodiment,the piston members are prevented from being inclined and can be alwaysmoved smoothly even if the piston members are rotatably received in thecompression chambers.

Although an example having one compressed air producing section and anexample having two compressed air producing sections are described inthe above embodiments, modifications may be made as needed. For example,more than two compressed air producing sections may be provided.

In the second, third and fourth embodiments having two compressed airproducing sections, the second pin insertion hole 95 has an arcuateslit-like sliding groove 95 a so that the rollers 37 and 37 of the firstand second compressed air producing sections 1 a and 1 b can constantlyrun on the cam face 91 a of the cam 9 with the retention pins 36 and 36of the first and second compressed air producing sections 1 a and 1 bretained by one piston retaining part 92. The present invention is,however, not limited thereto and may be modified as needed.

For example, when the retention pin 36 of the first compressed airproducing section 1 a is retained by a first piston retaining part andthe retention pin 36 of the second compressed air producing section 1 bis retained by a second piston retaining part, the first and second pininsertion holes 92 b and 95 may be circular holes.

When the retention pins 36 and 36 of the first and second compressed airproducing section 1 a and 1 b are retained by one piston retaining part92, the shapes and so on of the first and second pin insertion holes 92b and 95 are not limited to those shown in FIG. 13B and may be differentas long as the rollers 37 and 37 of the first and second compressed airproducing sections 1 a and 1 b can constantly run on the cam face 91 aof the cam 9 with the retention pins 36 and 36 of the first and secondcompressed air producing sections 1 a and 1 b retained by the pistonretaining part 92. The detail will be described below.

The plurality of compressed air producing sections are attached to thehub such that the piston members thereof can be slid in directionstoward and away from the axle when the wheel body is rotated about theaxle. The cam has a cam body provided with a cam face having a circularcross-section and in contact with the piston members on its outerperiphery, and a piston retaining part as an operation element retainingpart located on one side of the cam face of the cam for rotation withrespect to the cam body. The cam body is attached to the axle with thecenter of the cam face offset from the axis of the axle. The pistonretaining part has a plurality of pin insertion holes for retaining theretention pins of the compressed air producing sections. Two of the pininsertion holes are formed such that the two retention pins retained inthe two pin insertion holes can be relatively moved in thecircumferential direction of the cam face through at least an angle of 4sin⁻¹{e/r·sin(θ/2)} in total about the center of the cam face, wherein rrepresents the effective radius of the cam body, e represents the amountof offset from the axis of the axle to the center of the cam face of thecam body, and θ represents the angle formed by the sliding directions ofthe two piston members. The effective radius is the distance from thecenter of the cam face to the axes of the retention pins for retainingthe rollers of the piston members.

For example, as shown in FIG. 27, two piston members 32 and 32 can beslid in directions toward and away from the axle 101, and the angleformed by the sliding directions p1 and p2 of the piston members 32 and32 and the effective radius of the cam body 91 are defined as θ and e,respectively. The angle formed by the line connecting the center O1 ofthe cam face 91 a and the axis of the retention pin 36 of one of thepiston members 32 and the line connecting the center O1 of the cam face91 a and the axis of the retention pin 36 of the other piston member 32is defined as β. In FIG. 27, the piston members 32 and 32 are notrotated and the cam body 91 is rotated about the axis O3 of the axle 101as a center O3 of rotation for convenience of explanation.

Then, as shown in FIG. 27, when a shortest radius line w1 connecting theshortest point 91 b where the distance from the center O3 of rotation tothe cam face 91 a is minimum and the rotation center O3 comes to aposition where it divides the angle θ into two equal angles, the angle βhas a minimum value β1.

When the cam body 91 is rotated by 180° from the above state (to aposition indicated by dot-dash lines in FIG. 27) and a longest radiusline w2 connecting the longest point 91 c where the distance from thecenter O3 of rotation to the cam face 91 a is maximum and the rotationcenter O3 comes to a position where it divides the angle θ into twoequal angles, the angle β has a maximum value β2.

Thus, when the two piston members 32 and 32 are retained by one pistonretaining part 92 via retention pins 36 and 36, it is necessary that theretention pins 36 and 36 can be moved with respect to the pistonretaining part by the difference between the maximum angle β2 and theminimum angle β1 when the piston members 32 are rotated with respect tothe cam body 91.

That is, the pin insertion hole 95 has to be formed such that theretention pins 36 and 36 can be relatively moved with respect to thepiston retaining part 92 within an angle range of (β2−β1)=angle Ψ (seeFIG. 13).

As can be understood from FIG. 27, (β1)/2=θ/2−sin⁻¹{(e/r)·sin(π−θ/2)}and (β2)/2=θ/2+sin⁻¹{(e/r)·sin (θ/2)}. Thus, β2−β1=4sin⁻¹{(e/r)·sin(θ/2)}.

As described above, when retention pins 36 and 36 of a plurality ofcompressed air producing sections 1 a and 1 b are retained by one pistonretaining part 92, the first and second pin insertion holes 92 b and 95have to be formed such that the two retention pins 36 and 36 can berelatively moved through at least an angle of 4 sin⁻¹{(e/r)·sin(θ/2)} intotal about the center O1 of the cam face 91 a. When only the second pininsertion hole 95 has a sliding groove 95 a in which the retention pin36 can be slid, for example, as shown in FIG. 13B, the sliding groove 95a of the second pin insertion hole 95 has to extend through an angle Ψof 4 sin⁻¹{(e/r)·sin(θ/2)} or greater. In the embodiment shown in FIG.13B, θ is approximately 180°, e is approximately 2.2 mm and r isapproximately 14.2 mm. Thus, the angle Ψ is approximately 72°.

When a first pin insertion hole 940 and a second pin insertion hole 95have sliding grooves 940 a and 95 a, respectively, as shown in FIG. 26,the total of the angle Ψ1 through the sliding groove 940 a of the firstpin insertion hole 940 extends and the angle Ψ2 through which the pininsertion hole of the second pin insertion hole 95 extends (Ψ1+Ψ2) hasto be at least 4 sin⁻¹{e/r·sin(θ/2)}.

In FIG. 26, an example is shown in which the angle Ψ1 through which thesliding groove 940 a of the first pin insertion hole 940 extends and theangle Ψ2 through which the pin insertion hole 95 a of the second pininsertion hole 95 extends are generally the same. In FIG. 26, designatedas 940 b is a seat part of the first pin insertion hole 940 a formedaround the sliding groove 940 a. When more than two compressed airproducing sections are provided, the pin insertion holes have to beformed such that the retention pins of two of the compressed airproducing sections can be relatively moved through at least an angle of4 sin⁻¹{(e/r)·sin(θ/2)} in total about the center O1 of the cam face 91a.

When two compressed air producing sections are provided, the compressedair producing sections does not necessarily positioned at generallyequal intervals in the circumferential direction of the cam so that oneof the sliding parts is slid in the compression chamber from thelowermost position to the uppermost position when the other sliding partis slid in the compression chamber from the uppermost position to thelowermost position and modifications may be made as needed. However, itis advantageous to position the compressed air producing sections suchthat one of the sliding parts is slid in the compression chamber fromthe lowermost position to the uppermost position when the other slidingparts is slid in the compression chamber from the uppermost position tothe lowermost position since compressed air can be produced efficiently.

Although the retention pin 36 is moved in the second pin insertion hole95 together with the slider 80 in the above embodiments, the retentionpin 36 may be directly received in the second pin insertion hole 95 andmoved therein without the slider 80 when the piston member 32 isreceived in the compression chamber 31 in a non-rotatable manner in thesecond compressed air producing section 1 b.

When more than three compressed air producing sections are provided, thecompressed air producing sections may or may not positioned at generallyequal interval in the circumferential direction of the cam.

Although the compressed air produced in a compressed air producingsection is supplied to the saddle or brake device of the bicycle as apart other than the pneumatic tire through the another part compressedair supply passage in the above embodiments, the part other than thepneumatic tire is not limited to the saddle or brake device of thebicycle.

Although a pneumatic tire compressed air supply passage is provided inthe above embodiments, modifications may be made as needed. For example,the compressed air producing sections and the pneumatic tire may beconnected without the pneumatic tire compressed air supply passage sothat compressed air produced in the compressed air producing sectionscan be directly supplied to the pneumatic tire.

The automatic air-feeding mechanism of the present invention can beprovided on any vehicle having a wheel body rotatable about an axle. Forexample, the automatic air-feeding mechanism of the present invention isapplicable to one-wheeled vehicles, two-wheeled vehicles such asmotorcycles and rear cars, three- or four-wheeled vehicles of varioustypes and elevators having wheels.

Although the compressing element is the piston member 32 in the aboveembodiments, the present invention is not limited thereto and may bemodified as needed. For example, each compression chamber 31 may beextended into the interior of the hub 102 and provided with an elasticpart as a compressing element which forms the entire peripheral wall ofthe compression chamber 31 or a part of the peripheral wall of thecompression chamber 31 in the axial direction thereof and which can beexpanded and contracted, and a cam contact part formed at its proximalend and in contact with the cam face 91 a of the cam 9. When the hub 102is rotated, the cam contact part is slid on the cam face 91 a andpressed by the cam face 91 a, whereby the capacity of the compressionchamber 31 is brought into compressed state from an expanded state tocompress the air therein.

An automatic air-feeding mechanism for a pneumatic tire according to thepresent invention comprises a compressed air producing section whichproduces compressed air when a wheel body is rotated about an axle, andthe compressed air produced in the compressed air producing section issupplied to a pneumatic tire.

When the wheel body is rotated about the axle, compressed air isproduced in the compressed air producing section and the producedcompressed air is supplied to the pneumatic tire. Thus, when the wheelbody is rotated about the axle by, for example, riding the bicycle, thecompressing section automatically compresses air to a specific pressureand the compressed air is supplied to the pneumatic tire to keep the airpressure in the pneumatic tire constant.

The automatic air-feeding mechanism for a pneumatic tire according tothe present invention has a plurality of compressed air producingsections, each one of which has a compression chamber, a compressingelement for compressing the air in the compression chamber. Thecompressing elements are pressed by a cam mounted on the axle tocompress the air in the compression chamber when the wheel body isrotated about the axle. The compressed air producing sections arearranged such that the compressing elements of the compressed airproducing sections are pressed in sequence by the cam to perform thecompression of air when the wheel body is rotated about the axle.

When the wheel body is rotated about the axle, the plurality ofcompressed air producing sections can produce compressed air in anamount a plurality of times greater than the amount of compressed airthat can be produced by one compressed air producing section. Forexample, when a wheelchair is normally used, its travel distance is notlarge and the wheel is not rotated many times. Thus, when a wheelchairis driven for a short period of time, a sufficient amount of compressedair may not be supplied to the pneumatic tire. According to the presentinvention, however, a sufficient amount of compressed air can beproduced and supplied to the pneumatic tire until the air pressure inthe pneumatic tire reaches a specific level by the plurality ofcompressed air producing sections within a short period of time afterthe start of running even if the number of rotations of the wheel isstill low.

Also, since the compressing elements of the compressed air producingsections are pressed in sequence by the cam to perform the compressionof air when the wheel body is rotated about the axis, the force requiredto produce compressed air and the resistance applied to the rotation ofthe wheel body about the axle are smaller than those required andapplied when the air in the compression chambers are compressedsimultaneously.

For example, when a plurality of compressed air producing sections arearranged in different positions along the circumference of a cam, thecompressing elements of the compressed air producing sections arepressed in sequence by the cam when the wheel body is rotated about theaxle. That is, such a mechanism can be produced easily. Also, when theplurality of compressed air producing sections are arranged in thecircumferential direction of the cam, the axial length of the mechanismcan be short as a whole. Thus, since the automatic air-feeding mechanismcan be easily attached to the hub of a wheel body of a bicycle orwheelchair, it is suitable for a bicycle or wheelchair.

The automatic air-feeding mechanism for a pneumatic tire according tothe present invention further comprises an another part compressed airsupply passage for introducing compressed air produced in a compressionair producing section to a part of the vehicle other than the pneumatictire.

For example, compressed air produced in one of the compressed airproducing sections can be supplied to the pneumatic tire through apneumatic tire compressed air supply passage and compressed air producedin another compressed air producing section can be supplied to the airholding part of the saddle of the bicycle as the another part throughthe another part compressed air supply passage to provide the seat ofthe saddle with good cushion. Alternatively, compressed air can besupplied to a brake device of the bicycle through the another partcompressed air supply passage to prevent overheating of the brakedevice.

In the automatic air-feeding mechanism for a pneumatic tire according tothe present invention, the compressed air producing sections have firstand second compressed air producing sections, each one of which has thecompressing element provided with a sliding part slidable in thecompression chamber and a cam contact part in contact with the cam. Eachsliding part is slidable in a range between a lowermost position to makethe capacity of the compression chamber maximum and an uppermostposition to make the capacity of the compression chamber minimum. Whenthe wheel body is rotated about the axle, each cam contact part ispressed by the cam, whereby each sliding part is slid in the compressionchamber from the lowermost position to the uppermost position tocompress the air in the compression chamber. The first and secondcompressed air producing sections are arranged such that when thesliding part is slid in the compression chamber from the lowermostposition to the uppermost position in one of the first and secondcompressed air producing sections, the sliding part is slid in thecompression chamber from the uppermost position to the lowermostposition in the other compressed air producing section.

Then, the first and second compressed air producing sections alternatelycompress the air in their compression chambers, and when one of themcompresses air in its compression chamber, the other is not compressesthe air in its compression chamber. Thus, compressed air can be producedin an amount twice as much as the amount of compressed air that can beproduced in one compressed air producing section with generally the sameforce as the force necessary to produce compressed air in one compressedair producing section.

In an automatic air-feeding mechanism for a pneumatic tire according tothe present invention, the compressed air producing section has acompression chamber, a compressing element for compressing the air inthe compression chamber, and an air intake port for introducing outsideair into the compression chamber. The compressing element has a slidingpart slidable in the compression chamber in a range between a lowermostposition to make the capacity of the compression chamber maximum and anuppermost position to make the capacity of the compression chamberminimum. While the wheel body is being rotated about the axle, the airin the compression chamber is compressed when the sliding part is slidin the compression chamber from the lowermost position to the uppermostposition. The air intake port is provided in the vicinity of thelowermost position in the movable range of the sliding part slidable inthe compression chamber between the lowermost position and the uppermostposition.

Then, when the sliding part is slid in the compression chamber from thelowermost position to the uppermost position to compress the air in thecompression chamber, the air in the compression chamber can becompressed without being allowed to escape through the air intake portwhile the sliding part is slid from a position just beyond the airintake port to the uppermost position. Thus, since there is no need fora check valve for preventing air from escaping from the compressionchamber through the air intake port when the sliding part is slid in thecompression chamber to compress the air in the compression chamber, theautomatic air-feeding mechanism is simple in construction and hence canbe produced at low costs.

In the automatic air-feeding mechanism for a pneumatic tire according tothe present invention, the compressed air producing section is attachedto a hub of the wheel body, and can take in air into the compressionchamber from the interior of the hub and compress the air.

Since air can be introduced into the compression chamber from theinterior of the hub, where rainwater or the like can hardly enter, thereis little possibility of water entering the compression chamber togetherwith air.

In an automatic air feeding mechanism for a pneumatic tire according tothe present invention, the compressed air producing section has acompression chamber for compressing the air therein, an air intake portfor introducing outside air into the compression chamber, and awaterproof mechanism for preventing water from entering the compressionchamber through the air intake port.

Since the waterproof mechanism prevents rainwater or the like fromentering the compression chamber through the air intake-port togetherwith air even if the vehicle is used in rainy days, rainwater or thelike can be prevented from being fed from the compression chamber intothe pneumatic tire together with air.

In the automatic air-feeding mechanism for a pneumatic tire according tothe present invention, the wheel body has a hub rotatably supported bythe axle, and the compressed air producing section is attached to thehub of the wheel body. The waterproof mechanism has a first air passageconnecting the air intake port in air flow communication with theinterior of the hub so that air can be taken in from the interior of thehub into the compression chamber through the first air passage in orderto prevent water from entering the compressed air producing section.Since air can be introduced into the compression chamber from theinterior of the hub, where rainwater or the like can hardly enter, thereis little possibility of water entering the compression chamber togetherwith air. Thus, the waterproof mechanism can be easily constructed atlow costs.

In the automatic air-feeding mechanism for a pneumatic tire according tothe present invention, the hub has a cylindrical hub drum, andsupporting parts for supporting the hub drum from both sides. Thesupporting parts are rotatably supported on the axle, whereby the hub isrotatable about the axle and a partitioned space is defined in the hubby the hub drum and the supporting parts. The waterproof mechanism has asecond air passage formed through the supporting parts and communicatingthe partitioned space in the hub with the outside.

Then, rainwater or the like can hardly enter the partitioned spacethrough the second air passage. Thus, when air is fed from thepartitioned space toward the air intake port, water can be reliablyprevented from being fed together with the air.

In the automatic air-feeding mechanism for a pneumatic tire according tothe present invention, each one of the supporting parts of the hub has asteel ball receiving part for rotatably receiving a plurality of steelballs, and an axle hole formed radially inside the steel ball receivingpart for rotatably receiving the axle. The steel ball receiving partsare rotatably supported by the axle extending through the axle hole viaa plurality of steel balls, whereby the hub is rotatable about the axleand an axle-gap air passage extending from the partitioned space throughan axle gap formed between the inner surface of the axle hole and theaxle and steel ball gaps formed between the steel balls and in air flowcommunication with the partitioned space is formed through each of thesupporting parts of the hub. The second air passage includes at leastone of the axle-gap air passages as a constituent element.

The steel balls are usually provided in the steel ball receiving partstogether with grease for smooth rotation of the steel balls. Thus, watercan hardly pass through the gaps between the steel balls, which meanswater can hardly pass through the axle-gap air passages. An ordinary hubhas such axle-gap air passages. Thus, since the axle-gap air passagesformed in the hub can be used and there is no need to form a second airpassage separately, the waterproof mechanism can be constructed at lowcosts.

In the automatic air-feeding mechanism for a pneumatic tire according tothe present invention, one of the axle-gap air passages is generallysealed from the outside of the hub by a seal member and the otheraxle-gap air passage forms a part or the whole of the second airpassage. The waterproof mechanism has a third air passage communicatingthe other axle-gap air passage forming the second air passage with theoutside so that the air outside the hub can be introduced into the hubthrough the third air passage and the other axle-gap air passage.

Then, even if it costs much to form such a third air passage, a largeincrease in cost can be avoided since only one third air passage has tobe formed.

In the automatic air-feeding mechanism for a pneumatic tire according tothe present invention, the third air passage is defined between an innersurface of a cylindrical member which is attached to the hub and throughwhich the axle extends and an outer periphery of the axle, and the innersurface of the cylindrical member having a taper part which is taperedsuch that the inside diameter gradually increases toward the outside.

Then, even if water enters the third air passage, the water can be movedto the large-diameter side of the taper part and discharged out of thethird air passage by a centrifugal force created by the rotation of thehub. Also, the water can be moved outward on the taper part dischargedout of the third air passage by its own weight. Thus, water can hardlypass through the third air passage.

In an automatic air-feeding mechanism for a pneumatic tire according tothe present invention, the compressed air producing section has acompression chamber, and a compressing element for compressing the airin the compression chamber. The compressing element has a first endslidably received in the compression chamber and a second end retainedby a cam mounted on the axle, whereby, while the wheel body is beingrotated about the axle, the compressing element follows the cam and isslid in the compression chamber to compress the air in the compressionchamber.

When the compressing element is urged by a compressing element urgingcoil spring so that the second end of the compressing element can bekept in contact with the cam, for example, the compressing element hasto be slid against the urging force of the coil spring, causing aresistance to the rotation of the wheel body about the axle. In thisembodiment, however, the compressing element is retained by the cam andan urging coil spring is not provided, the compressing element can besmoothly slid with a small force. Thus, the resistance to the rotationof the wheel body about the axle is small.

In the automatic air-feeding mechanism for a pneumatic tire according tothe present invention, the compressing element is removably retained bythe cam.

Then, the compressed air producing section can be easily removed fromthe cam, and the compressed air producing section having removed fromthe cam can be easily assembled to the cam. Thus, since the parts can beeasily disassembled and replaced, maintenance can be made easily.

In the automatic air-feeding mechanism for a pneumatic tire according tothe present invention, the cam has a cam body having a cam face incontact with the compressing element on its outer periphery, and anoperation element retaining part located on one side of the cam face ofthe cam. The compressing element has a rod-like operation element, a camcontact part in contact with the cam face of the cam, and a camretention part retained by the operation element retaining part of thecam. The operation element is radially movably disposed radially outsidethe cam face of the cam body, the cam contact part is disposed betweenthe cam face of the cam body and the operation element, and the camretention part is removably retained by the operation element retainingpart.

Then, when the compressing element is pressed by the cam to performcompression of air, the operation element of the compressing element canbe pressed in a direction from inside to outside in a radial directionof the cam by the cam via the cam contact part. Thus, the operationelement can be moved in a radial direction of the cam smoothly andefficiently.

Also, the compressing element can be assembled to the cam by placing thecam retention part in the operation element retaining part located onone side of the cam face of the cam body and removed from the cam byremoving the cam retention part from the operation element retainingpart. Thus, the compressing element can be easily removed from the cam.When the cam retention part is retained by the operation elementretaining part located on one side of the cam face of the cam body, thecompressing element is pulled at one side when it is pulled by the cam.However, when the compressing element is pulled by the cam, a largeforce is not applied to the operation element since compression of airis not performed. Thus, the operation element can be smoothly pulledwithout difficulty.

In the automatic air-feeding mechanism for a pneumatic tire according tothe present invention, the cam contact part is constituted of a part ofthe outer periphery of a roller rotatably attached to the operationelement, and the cam retention part is constituted of a retention pinrotatably supporting the roller on the operation element and retained bythe operation element retaining part of the cam.

Then, the force in a tangential direction of the cam face which isapplied to the cam contact part when the compressing element is pressedcan be small, and the operation element of the compressing element canbe moved in a radial direction of the cam more efficiently and moresmoothly.

Also, since the retention pin for rotatably supporting the roller on theoperation element is used as a cam retention part retained by theoperation element retaining part of the cam, there is no need to form acam retention part separately. Thus, the automatic air-feeding mechanismcan be easily produced at low costs.

Description has been made of the preferred embodiments of the presentinvention. The terminology employed herein is for the purpose ofillustration but not of limitation. It should be understood that manychanges and modifications can be made within the scope of the appendedclaims without departing from the scope and spirit of the presentinvention.

1. An automatic air-feeding mechanism for a pneumatic tire forautomatically supplying air to a pneumatic tire mounted on a wheel bodyrotatable about an axle of a vehicle, comprising: a compressed airproducing section for producing compressed air when the wheel body isrotated about the axle, wherein the compressed air produced in thecompressed air producing section is supplied to the pneumatic tire. 2.The automatic air-feeding mechanism for a pneumatic tire as set forth inclaim 1, wherein a plurality of the compressed air producing sectionsare provided; each one of the compressed air producing sections has acompression chamber, and a compressing element for compressing the airin the compression chamber; wherein the compressing elements are pressedby a cam mounted on the axle to compress the air in the compressionchamber when the wheel body is rotated about the axle; and thecompressed air producing sections are arranged such that the compressingelements of the compressed air producing sections are pressed insequence by the cam to perform the compression of air when the wheelbody is rotated about the axle.
 3. The automatic air-feeding mechanismfor a pneumatic tire as set forth in claim 1, further comprising ananother part compressed air supply passage for introducing compressedair produced in the compression air producing section to a part of thevehicle other than the pneumatic tire.
 4. The automatic air-feedingmechanism for a pneumatic tire as set forth in claim 2, wherein thecompressed air producing sections have first and second compressed airproducing sections; each one of the first and second compressed airproducing sections has the compressing element provided with a slidingpart slidable in the compression chamber and a cam contact part incontact with the cam; each sliding part is slidable in a range between alowermost position to make the capacity of the compression chambermaximum and an uppermost position to make the capacity of thecompression chamber minimum; when the wheel body is rotated about theaxle, each cam contact part is pressed by the cam, whereby each slidingpart is slid in the compression chamber from the lowermost position tothe uppermost position to compress the air in the compression chamber;and the first and second compressed air producing sections are arrangedsuch that when the sliding part is slid in the compression chamber fromthe lowermost position to the uppermost position in one of the first andsecond compressed air producing sections, the sliding part is slid inthe compression chamber from the uppermost position to the lowermostposition in the other compressed air producing section.
 5. The automaticair-feeding mechanism for a pneumatic tire as set forth in claim 1;wherein the compressed air producing section has a compression chamber,a compressing element for compressing the air in the compressionchamber, and an air intake port for introducing outside air into thecompression chamber, the compressing element has a sliding part slidablein the compression chamber in a range between a lowermost position tomake the capacity of the compression chamber maximum and an uppermostposition to make the capacity of the compression chamber minimum, andwhile the wheel body is being rotated about the axle, the air in thecompression chamber is compressed when the sliding part is slid in thecompression chamber from the lowermost position to the uppermostposition; and the air intake port is provided in the vicinity of thelowermost position in the movable range of the sliding part slidable inthe compression chamber between the lowermost position and the uppermostposition.
 6. The automatic air-feeding mechanism for a pneumatic tire asset forth in claim 1, wherein the compressed air producing section isattached to a hub of the wheel body, and capable of taking air into thecompression chamber from the interior of the hub and compressing theair.
 7. The automatic air-feeding mechanism for a pneumatic tire as setforth in claim 1, wherein the compressed air producing section has acompression chamber for compressing the air therein, an air intake portfor introducing outside air into the compression chamber, and awaterproof mechanism for preventing water from entering the compressionchamber through the air intake port.
 8. The automatic air-feedingmechanism for a pneumatic tire as set forth in claim 7, wherein thewheel body has a hub rotatably supported by the axle; the compressed airproducing section is attached to the hub of the wheel body, and thewaterproof mechanism has a first air passage connecting the air intakeport in air flow communication with the interior of the hub so that aircan be taken in from the interior of the hub into the compressionchamber through the first air passage in order to prevent water fromentering the compressed air producing section.
 9. The automaticair-feeding mechanism for a pneumatic tire as set forth in claim 8,wherein the hub has a cylindrical hub drum, and supporting parts forsupporting the hub drum from both sides, the supporting parts beingrotatably supported on the axle, whereby the hub is rotatable about theaxle and a partitioned space is defined in the hub by the hub drum andthe supporting parts; and the waterproof mechanism has a second airpassage formed through the supporting parts and communicating thepartitioned space in the hub with the outside.
 10. The automaticair-feeding mechanism for a pneumatic tire as set forth in claim 9,wherein each one of the supporting parts of the hub has a steel ballreceiving part for rotatably receiving a plurality of steel balls, andan axle hole formed radially inside the steel ball receiving part forrotatably receiving the axle, and the steel ball receiving parts arerotatably supported by the axle extending through the axle hole via aplurality of steel balls, whereby the hub is rotatable about the axleand an axle-gap air passage extending from the partitioned space throughan axle gap formed between the inner surface of the axle hole and theaxle and steel ball gaps formed between the steel balls and in air flowcommunication with the partitioned space is formed through each of thesupporting parts of the hub; and the second air passage includes atleast one of the axle-gap air passages as a constituent element.
 11. Theautomatic air-feeding mechanism for a pneumatic tire as set forth inclaim 10, wherein one of the axle-gap air passages is generally sealedfrom the outside of the hub by a seal member and the other axle-gap airpassage forms a part or the whole of the second air passage; and thewaterproof mechanism has a third air passage communicating the otheraxle-gap air passage forming the second air passage with the outside sothat the air outside the hub can be introduced into the hub through thethird air passage and the other axle-gap air passage.
 12. The automaticair-feeding mechanism for a pneumatic tire as set forth in claim 11,wherein the third air passage is defined between an inner surface of acylindrical member which is attached to the hub and through which theaxle extends and an outer periphery of the axle; the inner surface ofthe cylindrical member has a taper part which is tapered such that theinside diameter gradually increases toward the outside.
 13. Theautomatic air-feeding mechanism for a pneumatic tire as set forth inclaim 1, wherein the compressed air producing section has a compressionchamber, and a compressing element for compressing the air in thecompression chamber; and the compressing element has a first endslidably received in the compression chamber and a second end retainedby a cam mounted on the axle, whereby, while the wheel body is beingrotated about the axle, the compressing element follows the cam and isslid in the compression chamber to compress the air in the compressionchamber.
 14. The automatic air-feeding mechanism for a pneumatic tire asset forth in claim 13, wherein the compressing element is removablyretained by the cam.
 15. The automatic air-feeding mechanism for apneumatic tire as set forth in claim 13, wherein the cam has a cam bodyhaving a cam face in contact with the compressing element on its outerperiphery, and an operation element retaining part located on one sideof the cam face of the cam body; and the compressing element has arod-like operation element, a cam contact part in contact with the camface of the cam, and a cam retention part retained by the operationelement retaining part of the cam, the operation element being radiallymovably disposed radially outside the cam face of the cam body, the camcontact part being disposed between the cam face of the cam body and theoperation element, the cam retention part being removably retained bythe operation element retaining part.
 16. The automatic air-feedingmechanism for a pneumatic tire as set forth in claim 15, wherein the camcontact part is constituted of a part of the outer periphery of a rollerrotatably attached to the operation element; and the cam retention partis constituted of a retention pin rotatably supporting the roller on theoperation element and retained by the operation element retaining partof the cam.